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Commit 091d0d55 authored May 09, 2013 by Li Zefan Committed by Linus Torvalds May 09, 2013

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 af73e4d9 ("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>

parent de2657f9

ipc/shm.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -493,7 +493,13 @@ static int newseg(struct ipc_namespace ns, struct ipc_params params)
		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)

mm/mmap.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1367,9 +1367,13 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
		len = ALIGN(len, huge_page_size(hstate_file(file)));
		} else if (flags & MAP_HUGETLB) {
		struct user_struct *user = NULL;
		struct hstate *hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) &
		SHM_HUGE_MASK);

		len = ALIGN(len, huge_page_size(hstate_sizelog(
		(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK)));
		if (!hs)
		return -EINVAL;

		len = ALIGN(len, huge_page_size(hs));
		/*
		* VM_NORESERVE is used because the reservations will be
		* taken when vm_ops->mmap() is called