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authorPavel Emelianov <xemul@openvz.org>2007-07-31 00:38:48 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-31 15:39:40 -0700
commit7be77e20d59fc3dd3fdde31641e0bc821114d26b (patch)
tree558507e6fe540d1deddb2dbce9b3a7cca855a57e /ipc
parentad0b142772eb1f88f0e77cb63c38b0005e83c2bd (diff)
downloadlinaro-lsk-7be77e20d59fc3dd3fdde31641e0bc821114d26b.tar.gz
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')
-rw-r--r--ipc/shm.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index d88ac5a07ec..a86a3a5c8a1 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;
}