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author | Pavel Emelianov <xemul@openvz.org> | 2007-07-31 11:38:48 +0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-08-10 01:27:36 +0400 |
commit | 68a0460bbcc7571753b57b83f21e8c1c5029a46a (patch) | |
tree | 89b04b034309ce8ea3c640466a8cdc1406a226e1 | |
parent | df358e1bad63f47ef3d399f8193bdc5a59d3d747 (diff) | |
download | linux-68a0460bbcc7571753b57b83f21e8c1c5029a46a.tar.xz |
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-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 0852f206d895..3bdcb9a19910 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; } |