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execve fixes for v6.11-rc4

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- binfmt_flat: Fix corruption when not offsetting data start
 
 - exec: Fix ToCToU between perm check and set-uid/gid usage
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Merge tag 'execve-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull execve fixes from Kees Cook:

 - binfmt_flat: Fix corruption when not offsetting data start

 - exec: Fix ToCToU between perm check and set-uid/gid usage

* tag 'execve-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  exec: Fix ToCToU between perm check and set-uid/gid usage
  binfmt_flat: Fix corruption when not offsetting data start
This commit is contained in:
Linus Torvalds 2024-08-13 16:10:32 -07:00
commit 6b0f8db921
2 changed files with 10 additions and 2 deletions
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4
fs/binfmt_flat.c
View File

@ -72,8 +72,10 @@
#ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET
#define DATA_START_OFFSET_WORDS (0)
#define MAX_SHARED_LIBS_UPDATE (0)
#else
#define DATA_START_OFFSET_WORDS (MAX_SHARED_LIBS)
#define MAX_SHARED_LIBS_UPDATE (MAX_SHARED_LIBS)
#endif
struct lib_info {
@ -880,7 +882,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
return res;
/* Update data segment pointers for all libraries */
for (i = 0; i < MAX_SHARED_LIBS; i++) {
for (i = 0; i < MAX_SHARED_LIBS_UPDATE; i++) {
if (!libinfo.lib_list[i].loaded)
continue;
for (j = 0; j < MAX_SHARED_LIBS; j++) {

8
fs/exec.c
View File

@ -1692,6 +1692,7 @@ static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
unsigned int mode;
vfsuid_t vfsuid;
vfsgid_t vfsgid;
int err;
if (!mnt_may_suid(file->f_path.mnt))
return;
@ -1708,12 +1709,17 @@ static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
/* Be careful if suid/sgid is set */
inode_lock(inode);
/* reload atomically mode/uid/gid now that lock held */
/* Atomically reload and check mode/uid/gid now that lock held. */
mode = inode->i_mode;
vfsuid = i_uid_into_vfsuid(idmap, inode);
vfsgid = i_gid_into_vfsgid(idmap, inode);
err = inode_permission(idmap, inode, MAY_EXEC);
inode_unlock(inode);
/* Did the exec bit vanish out from under us? Give up. */
if (err)
return;
/* We ignore suid/sgid if there are no mappings for them in the ns */
if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
!vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))