[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH 8/8] qcow2: Read outside array bounds in qcow2_p

From: Liam Merwick
Subject: Re: [Qemu-devel] [PATCH 8/8] qcow2: Read outside array bounds in qcow2_pre_write_overlap_check()
Date: Fri, 31 Aug 2018 14:32:05 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 30/08/18 19:43, Eric Blake wrote:
On 08/30/2018 10:47 AM, Liam Merwick wrote:
The commit for 0e4e4318eaa5 increments QCOW2_OL_MAX_BITNR but does not
add an array entry for QCOW2_OL_BITMAP_DIRECTORY_BITNR to metadata_ol_names[].
As a result, an array dereference of metadata_ol_names[8] in
qcow2_pre_write_overlap_check() could result in a read outside of the array bounds.

Fixes: 0e4e4318eaa5 ('qcow2: add overlap check for bitmap directory')

Cc: Vladimir Sementsov-Ogievskiy <address@hidden>
Signed-off-by: Liam Merwick <address@hidden>
Reviewed-by: Darren Kenny <address@hidden>
Reviewed-by: Mark Kanda <address@hidden>
  block/qcow2-refcount.c | 17 +++++++++--------
  1 file changed, 9 insertions(+), 8 deletions(-)

The fix looks correct, but to prevent the problem from happening again, I'd suggest you also add a compile-time BUG_ON that fails if the array size gets out of sync again due to another addition of another overlap detection bit.

Good idea. There is no generic BUG_ON in QEMU (just a few private copies) or BUILD_BUG_ON. I can add a commit that introduces a copy of include/linux/build_bug.h from the Linux kernel and use BUILD_BUG_ON in this commit. Is there any reason not to do that?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]