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author | Pavel Emelianov <xemul@openvz.org> | 2007-07-31 09:38:48 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-08-01 00:39:40 +0200 |
commit | 7be77e20d59fc3dd3fdde31641e0bc821114d26b (patch) | |
tree | 558507e6fe540d1deddb2dbce9b3a7cca855a57e /ipc/shm.c | |
parent | kbuild: whitelist references from __dbe_table to .init (diff) | |
download | linux-7be77e20d59fc3dd3fdde31641e0bc821114d26b.tar.xz linux-7be77e20d59fc3dd3fdde31641e0bc821114d26b.zip |
Fix user struct leakage with locked IPC shem segment
When user locks an ipc shmem segmant with SHM_LOCK ctl and the segment is
already locked the shmem_lock() function returns 0. After this the
subsequent code leaks the existing user struct:
== ipc/shm.c: sys_shmctl() ==
...
err = shmem_lock(shp->shm_file, 1, user);
if (!err) {
shp->shm_perm.mode |= SHM_LOCKED;
shp->mlock_user = user;
}
...
==
Other results of this are:
1. the new shp->mlock_user is not get-ed and will point to freed
memory when the task dies.
2. the RLIMIT_MEMLOCK is screwed on both user structs.
The exploit looks like this:
==
id = shmget(...);
setresuid(uid, 0, 0);
shmctl(id, SHM_LOCK, NULL);
setresuid(uid + 1, 0, 0);
shmctl(id, SHM_LOCK, NULL);
==
My solution is to return 0 to the userspace and do not change the
segment's user.
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/shm.c')
-rw-r--r-- | ipc/shm.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index d88ac5a07ec7..a86a3a5c8a19 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -716,7 +716,7 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) struct user_struct * user = current->user; if (!is_file_hugepages(shp->shm_file)) { err = shmem_lock(shp->shm_file, 1, user); - if (!err) { + if (!err && !(shp->shm_perm.mode & SHM_LOCKED)){ shp->shm_perm.mode |= SHM_LOCKED; shp->mlock_user = user; } |