cred: simpler, 1D supplementary groups

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>

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index 437e611592790b0ed725998d08281be420fcf954..0f9cd90c11af6173d78d4ace43465cc70332b18f 100644 (file)
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -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;

diff --git a/drivers/staging/lustre/lustre/ptlrpc/sec.c b/drivers/staging/lustre/lustre/ptlrpc/sec.c
index 5d3995d5c69af9f26718b5ba7f1245e8b2917bcd..a7416cd9ac71777424aee2101c5993b2447435d2 100644 (file)
--- a/drivers/staging/lustre/lustre/ptlrpc/sec.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/sec.c
@@ -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);
 

diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c
index 9d46a0bdd9f9aea4d882a77ac3c22454d0f2b634..62469c60be23263f21903fadc2217488c7160ed6 100644 (file)
--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -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);

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index a204d7e109d4d63a76d01a31198b00f3f1cd09be..39bfaba9c99c932a3ea8cf7005cb014d4dcd175f 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -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;
 }

diff --git a/fs/proc/array.c b/fs/proc/array.c
index d25b44601b30e27a0ab99e5d16b15e701af6bb72..89600fd5963d46d5a5bd0915bde36850f7e71110 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -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, ' ');

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 257db64562e54092adec7bc506b6db7325f86c3e..f0e70a1bb3acfe784148ba468a3577d23065a9a7 100644 (file)
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -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
  *

diff --git a/kernel/groups.c b/kernel/groups.c
index 74d431d252515042296bb739cb8aba456635113e..2fcadd66a8fd7cba19e264c6542ec8940a248a73 100644 (file)
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -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;
-
-       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)
+       struct group_info *gi;
+       unsigned int len;
+
+       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;

diff --git a/kernel/uid16.c b/kernel/uid16.c
index d58cc4d8f0d1fa95c7ec0120cb408a9b4ad859e5..cc40793464e3ca1959c9960a3cdbc3180d4c468b 100644 (file)
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -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;

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 66ddcb60519a169c02b4f5041d1bf1df731763b8..7cf7d6e380c2c87ecccb11bae3f677676062d11f 100644 (file)
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -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;

diff --git a/net/sunrpc/auth_generic.c b/net/sunrpc/auth_generic.c
index 168219535a341056c22679273771dcf7d7656f28..83dffeadf20acbec87e93ef96fdad20d80e8f630 100644 (file)
--- a/net/sunrpc/auth_generic.c
+++ b/net/sunrpc/auth_generic.c
@@ -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:

diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c
index eeeba5adee6d939ab3429100d231a46e82b1ff94..dc6fb79a361f1ca3ab9869fc02ba05c1a533ad9b 100644 (file)
--- a/net/sunrpc/auth_gss/gss_rpc_xdr.c
+++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c
@@ -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;

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index d8582028b34600dc20e4447a99aeb5384b9ecb54..d67f7e1bc82ddc55f6f9927343387f20fa81fa32 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -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 */

diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index a99278c984e82a2156c20e3a4a7fa174783b9297..a1d768a973f5297a60899d475763d184228010db 100644 (file)
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -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;

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index dfacdc95b3f52010b3342c53dbd06788f1378128..64af4f034de693f921faf3f818d833e868b0a2e2 100644 (file)
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -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;