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cred: simpler, 1D supplementary groups

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Current supplementary groups code can massively overallocate memory and
is implemented in a way so that access to individual gid is done via 2D
array.

If number of gids is <= 32, memory allocation is more or less tolerable
(140/148 bytes).  But if it is not, code allocates full page (!)
regardless and, what's even more fun, doesn't reuse small 32-entry
array.

2D array means dependent shifts, loads and LEAs without possibility to
optimize them (gid is never known at compile time).

All of the above is unnecessary.  Switch to the usual
trailing-zero-len-array scheme.  Memory is allocated with
kmalloc/vmalloc() and only as much as needed.  Accesses become simpler
(LEA 8(gi,idx,4) or even without displacement).

Maximum number of gids is 65536 which translates to 256KB+8 bytes.  I
think kernel can handle such allocation.

On my usual desktop system with whole 9 (nine) aux groups, struct
group_info shrinks from 148 bytes to 44 bytes, yay!

Nice side effects:

 - "gi->gid[i]" is shorter than "GROUP_AT(gi, i)", less typing,

 - fix little mess in net/ipv4/ping.c
   should have been using GROUP_AT macro but this point becomes moot,

 - aux group allocation is persistent and should be accounted as such.

Link: http://lkml.kernel.org/r/20160817201927.GA2096@p183.telecom.by
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Vasily Kulikov <segoon@openwall.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2016-10-07 17:03:12 -07:00 committed by Linus Torvalds
parent 954f74bf45
commit 81243eacfa
14 changed files with 45 additions and 84 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/s390/kernel/compat_linux.c
View File

@ -189,7 +189,7 @@ static int groups16_to_user(u16 __user *grouplist, struct group_info *group_info
kgid_t kgid;
for (i = 0; i < group_info->ngroups; i++) {
kgid = GROUP_AT(group_info, i);
kgid = group_info->gid[i];
group = (u16)from_kgid_munged(user_ns, kgid);
if (put_user(group, grouplist+i))
return -EFAULT;
@ -213,7 +213,7 @@ static int groups16_from_user(struct group_info *group_info, u16 __user *groupli
if (!gid_valid(kgid))
return -EINVAL;
GROUP_AT(group_info, i) = kgid;
group_info->gid[i] = kgid;
}
return 0;

2
drivers/staging/lustre/lustre/ptlrpc/sec.c
View File

@ -2220,7 +2220,7 @@ int sptlrpc_pack_user_desc(struct lustre_msg *msg, int offset)
task_lock(current);
if (pud->pud_ngroups > current_ngroups)
pud->pud_ngroups = current_ngroups;
memcpy(pud->pud_groups, current_cred()->group_info->blocks[0],
memcpy(pud->pud_groups, current_cred()->group_info->gid,
pud->pud_ngroups * sizeof(__u32));
task_unlock(current);

6
fs/nfsd/auth.c
View File

@ -55,10 +55,10 @@ int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
goto oom;
for (i = 0; i < rqgi->ngroups; i++) {
if (gid_eq(GLOBAL_ROOT_GID, GROUP_AT(rqgi, i)))
GROUP_AT(gi, i) = exp->ex_anon_gid;
if (gid_eq(GLOBAL_ROOT_GID, rqgi->gid[i]))
gi->gid[i] = exp->ex_anon_gid;
else
GROUP_AT(gi, i) = GROUP_AT(rqgi, i);
gi->gid[i] = rqgi->gid[i];
}
} else {
gi = get_group_info(rqgi);

2
fs/nfsd/nfs4state.c
View File

@ -1903,7 +1903,7 @@ static bool groups_equal(struct group_info *g1, struct group_info *g2)
if (g1->ngroups != g2->ngroups)
return false;
for (i=0; i<g1->ngroups; i++)
if (!gid_eq(GROUP_AT(g1, i), GROUP_AT(g2, i)))
if (!gid_eq(g1->gid[i], g2->gid[i]))
return false;
return true;
}

2
fs/proc/array.c
View File

@ -207,7 +207,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
group_info = cred->group_info;
for (g = 0; g < group_info->ngroups; g++)
seq_put_decimal_ull(m, g ? " " : "",
from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
from_kgid_munged(user_ns, group_info->gid[g]));
put_cred(cred);
/* Trailing space shouldn't have been added in the first place. */
seq_putc(m, ' ');

11
include/linux/cred.h
View File

@ -26,15 +26,10 @@ struct inode;
/*
* COW Supplementary groups list
*/
#define NGROUPS_SMALL 32
#define NGROUPS_PER_BLOCK ((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))
struct group_info {
atomic_t usage;
int ngroups;
int nblocks;
kgid_t small_block[NGROUPS_SMALL];
kgid_t *blocks[0];
kgid_t gid[0];
};
/**
@ -88,10 +83,6 @@ extern void set_groups(struct cred *, struct group_info *);
extern int groups_search(const struct group_info *, kgid_t);
extern bool may_setgroups(void);
/* access the groups "array" with this macro */
#define GROUP_AT(gi, i) \
((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
/*
* The security context of a task
*

65
kernel/groups.c
View File

@ -7,55 +7,31 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/user_namespace.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
struct group_info *groups_alloc(int gidsetsize)
{
struct group_info *group_info;
int nblocks;
int i;
struct group_info *gi;
unsigned int len;
nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
/* Make sure we always allocate at least one indirect block pointer */
nblocks = nblocks ? : 1;
group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
if (!group_info)
len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize;
gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY);
if (!gi)
gi = __vmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_HIGHMEM, PAGE_KERNEL);
if (!gi)
return NULL;
group_info->ngroups = gidsetsize;
group_info->nblocks = nblocks;
atomic_set(&group_info->usage, 1);
if (gidsetsize <= NGROUPS_SMALL)
group_info->blocks[0] = group_info->small_block;
else {
for (i = 0; i < nblocks; i++) {
kgid_t *b;
b = (void *)__get_free_page(GFP_USER);
if (!b)
goto out_undo_partial_alloc;
group_info->blocks[i] = b;
}
}
return group_info;
out_undo_partial_alloc:
while (--i >= 0) {
free_page((unsigned long)group_info->blocks[i]);
}
kfree(group_info);
return NULL;
atomic_set(&gi->usage, 1);
gi->ngroups = gidsetsize;
return gi;
}
EXPORT_SYMBOL(groups_alloc);
void groups_free(struct group_info *group_info)
{
if (group_info->blocks[0] != group_info->small_block) {
int i;
for (i = 0; i < group_info->nblocks; i++)
free_page((unsigned long)group_info->blocks[i]);
}
kfree(group_info);
kvfree(group_info);
}
EXPORT_SYMBOL(groups_free);
@ -70,7 +46,7 @@ static int groups_to_user(gid_t __user *grouplist,
for (i = 0; i < count; i++) {
gid_t gid;
gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
gid = from_kgid_munged(user_ns, group_info->gid[i]);
if (put_user(gid, grouplist+i))
return -EFAULT;
}
@ -95,7 +71,7 @@ static int groups_from_user(struct group_info *group_info,
if (!gid_valid(kgid))
return -EINVAL;
GROUP_AT(group_info, i) = kgid;
group_info->gid[i] = kgid;
}
return 0;
}
@ -115,15 +91,14 @@ static void groups_sort(struct group_info *group_info)
for (base = 0; base < max; base++) {
int left = base;
int right = left + stride;
kgid_t tmp = GROUP_AT(group_info, right);
kgid_t tmp = group_info->gid[right];
while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
GROUP_AT(group_info, right) =
GROUP_AT(group_info, left);
while (left >= 0 && gid_gt(group_info->gid[left], tmp)) {
group_info->gid[right] = group_info->gid[left];
right = left;
left -= stride;
}
GROUP_AT(group_info, right) = tmp;
group_info->gid[right] = tmp;
}
stride /= 3;
}
@ -141,9 +116,9 @@ int groups_search(const struct group_info *group_info, kgid_t grp)
right = group_info->ngroups;
while (left < right) {
unsigned int mid = (left+right)/2;
if (gid_gt(grp, GROUP_AT(group_info, mid)))
if (gid_gt(grp, group_info->gid[mid]))
left = mid + 1;
else if (gid_lt(grp, GROUP_AT(group_info, mid)))
else if (gid_lt(grp, group_info->gid[mid]))
right = mid;
else
return 1;

4
kernel/uid16.c
View File

@ -117,7 +117,7 @@ static int groups16_to_user(old_gid_t __user *grouplist,
kgid_t kgid;
for (i = 0; i < group_info->ngroups; i++) {
kgid = GROUP_AT(group_info, i);
kgid = group_info->gid[i];
group = high2lowgid(from_kgid_munged(user_ns, kgid));
if (put_user(group, grouplist+i))
return -EFAULT;
@ -142,7 +142,7 @@ static int groups16_from_user(struct group_info *group_info,
if (!gid_valid(kgid))
return -EINVAL;
GROUP_AT(group_info, i) = kgid;
group_info->gid[i] = kgid;
}
return 0;

15
net/ipv4/ping.c
View File

@ -258,7 +258,7 @@ int ping_init_sock(struct sock *sk)
struct net *net = sock_net(sk);
kgid_t group = current_egid();
struct group_info *group_info;
int i, j, count;
int i;
kgid_t low, high;
int ret = 0;
@ -270,16 +270,11 @@ int ping_init_sock(struct sock *sk)
return 0;
group_info = get_current_groups();
count = group_info->ngroups;
for (i = 0; i < group_info->nblocks; i++) {
int cp_count = min_t(int, NGROUPS_PER_BLOCK, count);
for (j = 0; j < cp_count; j++) {
kgid_t gid = group_info->blocks[i][j];
if (gid_lte(low, gid) && gid_lte(gid, high))
goto out_release_group;
}
for (i = 0; i < group_info->ngroups; i++) {
kgid_t gid = group_info->gid[i];
count -= cp_count;
if (gid_lte(low, gid) && gid_lte(gid, high))
goto out_release_group;
}
ret = -EACCES;

4
net/sunrpc/auth_generic.c
View File

@ -176,8 +176,8 @@ generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
goto out_nomatch;
for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
if (!gid_eq(GROUP_AT(gcred->acred.group_info, i),
GROUP_AT(acred->group_info, i)))
if (!gid_eq(gcred->acred.group_info->gid[i],
acred->group_info->gid[i]))
goto out_nomatch;
}
out_match:

2
net/sunrpc/auth_gss/gss_rpc_xdr.c
View File

@ -229,7 +229,7 @@ static int gssx_dec_linux_creds(struct xdr_stream *xdr,
kgid = make_kgid(&init_user_ns, tmp);
if (!gid_valid(kgid))
goto out_free_groups;
GROUP_AT(creds->cr_group_info, i) = kgid;
creds->cr_group_info->gid[i] = kgid;
}
return 0;

2
net/sunrpc/auth_gss/svcauth_gss.c
View File

@ -479,7 +479,7 @@ static int rsc_parse(struct cache_detail *cd,
kgid = make_kgid(&init_user_ns, id);
if (!gid_valid(kgid))
goto out;
GROUP_AT(rsci.cred.cr_group_info, i) = kgid;
rsci.cred.cr_group_info->gid[i] = kgid;
}
/* mech name */

4
net/sunrpc/auth_unix.c
View File

@ -79,7 +79,7 @@ unx_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags, gfp_t
cred->uc_gid = acred->gid;
for (i = 0; i < groups; i++)
cred->uc_gids[i] = GROUP_AT(acred->group_info, i);
cred->uc_gids[i] = acred->group_info->gid[i];
if (i < NFS_NGROUPS)
cred->uc_gids[i] = INVALID_GID;
@ -127,7 +127,7 @@ unx_match(struct auth_cred *acred, struct rpc_cred *rcred, int flags)
if (groups > NFS_NGROUPS)
groups = NFS_NGROUPS;
for (i = 0; i < groups ; i++)
if (!gid_eq(cred->uc_gids[i], GROUP_AT(acred->group_info, i)))
if (!gid_eq(cred->uc_gids[i], acred->group_info->gid[i]))
return 0;
if (groups < NFS_NGROUPS && gid_valid(cred->uc_gids[groups]))
return 0;

6
net/sunrpc/svcauth_unix.c
View File

@ -517,7 +517,7 @@ static int unix_gid_parse(struct cache_detail *cd,
kgid = make_kgid(&init_user_ns, gid);
if (!gid_valid(kgid))
goto out;
GROUP_AT(ug.gi, i) = kgid;
ug.gi->gid[i] = kgid;
}
ugp = unix_gid_lookup(cd, uid);
@ -564,7 +564,7 @@ static int unix_gid_show(struct seq_file *m,
seq_printf(m, "%u %d:", from_kuid_munged(user_ns, ug->uid), glen);
for (i = 0; i < glen; i++)
seq_printf(m, " %d", from_kgid_munged(user_ns, GROUP_AT(ug->gi, i)));
seq_printf(m, " %d", from_kgid_munged(user_ns, ug->gi->gid[i]));
seq_printf(m, "\n");
return 0;
}
@ -817,7 +817,7 @@ svcauth_unix_accept(struct svc_rqst *rqstp, __be32 *authp)
return SVC_CLOSE;
for (i = 0; i < slen; i++) {
kgid_t kgid = make_kgid(&init_user_ns, svc_getnl(argv));
GROUP_AT(cred->cr_group_info, i) = kgid;
cred->cr_group_info->gid[i] = kgid;
}
if (svc_getu32(argv) != htonl(RPC_AUTH_NULL) || svc_getu32(argv) != 0) {
*authp = rpc_autherr_badverf;