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authorDavidlohr Bueso <dave@stgolabs.net>2018-05-25 14:47:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-05-25 18:12:11 -0700
commit8f89c007b6dec16a1793cb88de88fcc02117bbbc (patch)
tree8fad454a036ae457f9329d884687da84ff2c5746 /ipc
parenta73ab244f0dad8fffb3291b905f73e2d3eaa7c00 (diff)
downloadlinux-stericsson-8f89c007b6dec16a1793cb88de88fcc02117bbbc.tar.gz
ipc/shm: fix shmat() nil address after round-down when remapping
shmat()'s SHM_REMAP option forbids passing a nil address for; this is in fact the very first thing we check for. Andrea reported that for SHM_RND|SHM_REMAP cases we can end up bypassing the initial addr check, but we need to check again if the address was rounded down to nil. As of this patch, such cases will return -EINVAL. Link: http://lkml.kernel.org/r/20180503204934.kk63josdu6u53fbd@linux-n805 Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Reported-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Joe Lawrence <joe.lawrence@redhat.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: <stable@vger.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.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index 930be3aa80cf..d73269381ec7 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1363,9 +1363,17 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
if (addr) {
if (addr & (shmlba - 1)) {
- if (shmflg & SHM_RND)
+ if (shmflg & SHM_RND) {
addr &= ~(shmlba - 1); /* round down */
- else
+
+ /*
+ * Ensure that the round-down is non-nil
+ * when remapping. This can happen for
+ * cases when addr < shmlba.
+ */
+ if (!addr && (shmflg & SHM_REMAP))
+ goto out;
+ } else
#ifndef __ARCH_FORCE_SHMLBA
if (addr & ~PAGE_MASK)
#endif