Add a reference to ucounts for each cred
For RLIMIT_NPROC and some other rlimits the user_struct that holds the global limit is kept alive for the lifetime of a process by keeping it in struct cred. Adding a pointer to ucounts in the struct cred will allow to track RLIMIT_NPROC not only for user in the system, but for user in the user_namespace. Updating ucounts may require memory allocation which may fail. So, we cannot change cred.ucounts in the commit_creds() because this function cannot fail and it should always return 0. For this reason, we modify cred.ucounts before calling the commit_creds(). Changelog v6: * Fix null-ptr-deref in is_ucounts_overlimit() detected by trinity. This error was caused by the fact that cred_alloc_blank() left the ucounts pointer empty. Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lkml.kernel.org/r/b37aaef28d8b9b0d757e07ba6dd27281bbe39259.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
parent
f9c82a4ea8
commit
905ae01c4a
@ -1360,6 +1360,10 @@ int begin_new_exec(struct linux_binprm * bprm)
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WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
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WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
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flush_signal_handlers(me, 0);
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flush_signal_handlers(me, 0);
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retval = set_cred_ucounts(bprm->cred);
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if (retval < 0)
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goto out_unlock;
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/*
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/*
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* install the new credentials for this executable
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* install the new credentials for this executable
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*/
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*/
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@ -144,6 +144,7 @@ struct cred {
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#endif
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#endif
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struct user_struct *user; /* real user ID subscription */
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struct user_struct *user; /* real user ID subscription */
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struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
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struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
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struct ucounts *ucounts;
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struct group_info *group_info; /* supplementary groups for euid/fsgid */
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struct group_info *group_info; /* supplementary groups for euid/fsgid */
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/* RCU deletion */
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/* RCU deletion */
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union {
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union {
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@ -170,6 +171,7 @@ extern int set_security_override_from_ctx(struct cred *, const char *);
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extern int set_create_files_as(struct cred *, struct inode *);
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extern int set_create_files_as(struct cred *, struct inode *);
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extern int cred_fscmp(const struct cred *, const struct cred *);
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extern int cred_fscmp(const struct cred *, const struct cred *);
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extern void __init cred_init(void);
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extern void __init cred_init(void);
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extern int set_cred_ucounts(struct cred *);
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/*
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/*
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* check for validity of credentials
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* check for validity of credentials
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@ -100,11 +100,15 @@ struct ucounts {
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};
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};
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extern struct user_namespace init_user_ns;
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extern struct user_namespace init_user_ns;
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extern struct ucounts init_ucounts;
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bool setup_userns_sysctls(struct user_namespace *ns);
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bool setup_userns_sysctls(struct user_namespace *ns);
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void retire_userns_sysctls(struct user_namespace *ns);
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void retire_userns_sysctls(struct user_namespace *ns);
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struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
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struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
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void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
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void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
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struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid);
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struct ucounts *get_ucounts(struct ucounts *ucounts);
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void put_ucounts(struct ucounts *ucounts);
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#ifdef CONFIG_USER_NS
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#ifdef CONFIG_USER_NS
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@ -60,6 +60,7 @@ struct cred init_cred = {
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.user = INIT_USER,
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.user = INIT_USER,
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.user_ns = &init_user_ns,
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.user_ns = &init_user_ns,
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.group_info = &init_groups,
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.group_info = &init_groups,
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.ucounts = &init_ucounts,
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};
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};
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static inline void set_cred_subscribers(struct cred *cred, int n)
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static inline void set_cred_subscribers(struct cred *cred, int n)
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@ -119,6 +120,8 @@ static void put_cred_rcu(struct rcu_head *rcu)
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if (cred->group_info)
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if (cred->group_info)
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put_group_info(cred->group_info);
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put_group_info(cred->group_info);
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free_uid(cred->user);
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free_uid(cred->user);
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if (cred->ucounts)
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put_ucounts(cred->ucounts);
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put_user_ns(cred->user_ns);
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put_user_ns(cred->user_ns);
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kmem_cache_free(cred_jar, cred);
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kmem_cache_free(cred_jar, cred);
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}
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}
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@ -222,6 +225,7 @@ struct cred *cred_alloc_blank(void)
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#ifdef CONFIG_DEBUG_CREDENTIALS
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#ifdef CONFIG_DEBUG_CREDENTIALS
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new->magic = CRED_MAGIC;
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new->magic = CRED_MAGIC;
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#endif
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#endif
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new->ucounts = get_ucounts(&init_ucounts);
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if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
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if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
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goto error;
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goto error;
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@ -284,6 +288,11 @@ struct cred *prepare_creds(void)
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if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
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if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
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goto error;
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goto error;
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new->ucounts = get_ucounts(new->ucounts);
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if (!new->ucounts)
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goto error;
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validate_creds(new);
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validate_creds(new);
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return new;
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return new;
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@ -363,6 +372,8 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
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ret = create_user_ns(new);
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ret = create_user_ns(new);
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if (ret < 0)
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if (ret < 0)
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goto error_put;
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goto error_put;
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if (set_cred_ucounts(new) < 0)
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goto error_put;
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}
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}
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#ifdef CONFIG_KEYS
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#ifdef CONFIG_KEYS
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@ -653,6 +664,31 @@ int cred_fscmp(const struct cred *a, const struct cred *b)
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}
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}
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EXPORT_SYMBOL(cred_fscmp);
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EXPORT_SYMBOL(cred_fscmp);
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int set_cred_ucounts(struct cred *new)
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{
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struct task_struct *task = current;
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const struct cred *old = task->real_cred;
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struct ucounts *old_ucounts = new->ucounts;
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if (new->user == old->user && new->user_ns == old->user_ns)
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return 0;
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/*
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* This optimization is needed because alloc_ucounts() uses locks
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* for table lookups.
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*/
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if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
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return 0;
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if (!(new->ucounts = alloc_ucounts(new->user_ns, new->euid)))
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return -EAGAIN;
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if (old_ucounts)
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put_ucounts(old_ucounts);
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return 0;
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}
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/*
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/*
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* initialise the credentials stuff
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* initialise the credentials stuff
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*/
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*/
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@ -719,6 +755,10 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
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if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
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if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
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goto error;
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goto error;
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new->ucounts = get_ucounts(new->ucounts);
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if (!new->ucounts)
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goto error;
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put_cred(old);
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put_cred(old);
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validate_creds(new);
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validate_creds(new);
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return new;
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return new;
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@ -2995,6 +2995,12 @@ int ksys_unshare(unsigned long unshare_flags)
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if (err)
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if (err)
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goto bad_unshare_cleanup_cred;
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goto bad_unshare_cleanup_cred;
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if (new_cred) {
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err = set_cred_ucounts(new_cred);
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if (err)
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goto bad_unshare_cleanup_cred;
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}
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if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
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if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
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if (do_sysvsem) {
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if (do_sysvsem) {
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/*
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/*
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12
kernel/sys.c
12
kernel/sys.c
@ -552,6 +552,10 @@ long __sys_setreuid(uid_t ruid, uid_t euid)
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if (retval < 0)
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if (retval < 0)
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goto error;
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goto error;
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retval = set_cred_ucounts(new);
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if (retval < 0)
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goto error;
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return commit_creds(new);
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return commit_creds(new);
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error:
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error:
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@ -610,6 +614,10 @@ long __sys_setuid(uid_t uid)
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if (retval < 0)
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if (retval < 0)
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goto error;
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goto error;
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retval = set_cred_ucounts(new);
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if (retval < 0)
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goto error;
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return commit_creds(new);
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return commit_creds(new);
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error:
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error:
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@ -685,6 +693,10 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
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if (retval < 0)
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if (retval < 0)
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goto error;
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goto error;
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retval = set_cred_ucounts(new);
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if (retval < 0)
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goto error;
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return commit_creds(new);
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return commit_creds(new);
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error:
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error:
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@ -8,6 +8,12 @@
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#include <linux/kmemleak.h>
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#include <linux/kmemleak.h>
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#include <linux/user_namespace.h>
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#include <linux/user_namespace.h>
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struct ucounts init_ucounts = {
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.ns = &init_user_ns,
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.uid = GLOBAL_ROOT_UID,
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.count = 1,
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};
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#define UCOUNTS_HASHTABLE_BITS 10
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#define UCOUNTS_HASHTABLE_BITS 10
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static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
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static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
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static DEFINE_SPINLOCK(ucounts_lock);
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static DEFINE_SPINLOCK(ucounts_lock);
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@ -125,7 +131,15 @@ static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struc
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return NULL;
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return NULL;
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}
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}
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static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
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static void hlist_add_ucounts(struct ucounts *ucounts)
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{
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struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid);
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spin_lock_irq(&ucounts_lock);
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hlist_add_head(&ucounts->node, hashent);
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spin_unlock_irq(&ucounts_lock);
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}
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struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
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{
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{
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struct hlist_head *hashent = ucounts_hashentry(ns, uid);
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struct hlist_head *hashent = ucounts_hashentry(ns, uid);
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struct ucounts *ucounts, *new;
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struct ucounts *ucounts, *new;
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@ -160,7 +174,26 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
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return ucounts;
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return ucounts;
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}
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}
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static void put_ucounts(struct ucounts *ucounts)
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struct ucounts *get_ucounts(struct ucounts *ucounts)
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{
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unsigned long flags;
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if (!ucounts)
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return NULL;
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spin_lock_irqsave(&ucounts_lock, flags);
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if (ucounts->count == INT_MAX) {
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WARN_ONCE(1, "ucounts: counter has reached its maximum value");
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ucounts = NULL;
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} else {
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ucounts->count += 1;
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}
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spin_unlock_irqrestore(&ucounts_lock, flags);
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return ucounts;
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}
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void put_ucounts(struct ucounts *ucounts)
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{
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{
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unsigned long flags;
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unsigned long flags;
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@ -194,7 +227,7 @@ struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
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{
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{
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struct ucounts *ucounts, *iter, *bad;
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struct ucounts *ucounts, *iter, *bad;
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struct user_namespace *tns;
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struct user_namespace *tns;
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ucounts = get_ucounts(ns, uid);
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ucounts = alloc_ucounts(ns, uid);
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for (iter = ucounts; iter; iter = tns->ucounts) {
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for (iter = ucounts; iter; iter = tns->ucounts) {
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long max;
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long max;
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tns = iter->ns;
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tns = iter->ns;
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@ -237,6 +270,7 @@ static __init int user_namespace_sysctl_init(void)
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BUG_ON(!user_header);
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BUG_ON(!user_header);
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BUG_ON(!setup_userns_sysctls(&init_user_ns));
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BUG_ON(!setup_userns_sysctls(&init_user_ns));
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#endif
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#endif
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hlist_add_ucounts(&init_ucounts);
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return 0;
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return 0;
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}
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}
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subsys_initcall(user_namespace_sysctl_init);
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subsys_initcall(user_namespace_sysctl_init);
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@ -1340,6 +1340,9 @@ static int userns_install(struct nsset *nsset, struct ns_common *ns)
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put_user_ns(cred->user_ns);
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put_user_ns(cred->user_ns);
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set_cred_user_ns(cred, get_user_ns(user_ns));
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set_cred_user_ns(cred, get_user_ns(user_ns));
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if (set_cred_ucounts(cred) < 0)
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return -EINVAL;
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return 0;
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return 0;
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}
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}
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Loading…
Reference in New Issue
Block a user