shm: fix null pointer deref when userspace specifies invalid hugepage size
Dave reported an oops triggered by trinity:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: newseg+0x10d/0x390
PGD cf8c1067 PUD cf8c2067 PMD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
CPU: 2 PID: 7636 Comm: trinity-child2 Not tainted 3.9.0+#67
...
Call Trace:
ipcget+0x182/0x380
SyS_shmget+0x5a/0x60
tracesys+0xdd/0xe2
This bug was introduced by commit af73e4d9506d ("hugetlbfs: fix mmap
failure in unaligned size request").
Reported-by: Dave Jones <davej@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Li Zefan <lizfan@huawei.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/shm.c b/ipc/shm.c
index 34af1fe..7e199fa 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -493,7 +493,13 @@
if (shmflg & SHM_HUGETLB) {
struct hstate *hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT)
& SHM_HUGE_MASK);
- size_t hugesize = ALIGN(size, huge_page_size(hs));
+ size_t hugesize;
+
+ if (!hs) {
+ error = -EINVAL;
+ goto no_file;
+ }
+ hugesize = ALIGN(size, huge_page_size(hs));
/* hugetlb_file_setup applies strict accounting */
if (shmflg & SHM_NORESERVE)