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authorPavel Emelianov <xemul@openvz.org>2007-07-31 00:38:48 -0700
committerWilly Tarreau <w@1wt.eu>2007-08-25 17:24:06 +0200
commitdd6de5b299db5ca6e81f3237bf61610921ab5933 (patch)
treedc19f2c814565a00c0e396d9636d1734a999332d
parent037f00bce0965f3291bf80595c6a0bcc33cca3a1 (diff)
[PATCH] 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> Signed-off-by: Willy Tarreau <w@1wt.eu>
-rw-r--r--ipc/shm.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index f8e10a25ad7d..10b7a2c3ea2e 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -652,7 +652,7 @@ 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;
}