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SubjectRe: [RFC 0/3] block: address blktrace use-after-free
On Wed, Apr 01, 2020 at 11:59:59PM +0000, Luis Chamberlain wrote:
> Upstream kernel.org korg#205713 contends that there is a UAF in
> the core debugfs debugfs_remove() function, and has gone through
> pushing for a CVE for this, CVE-2019-19770.
>
> If correct then parent dentries are not positive, and this would
> have implications far beyond this bug report. Thankfully, upon review
> with Nicolai, he wasn't buying it. His suspicions that this was just
> a blktrace issue were spot on, and this patch series demonstrates
> that, provides a reproducer, and provides a solution to the issue.
>
> We there would like to contend CVE-2019-19770 as invalid. The
> implications suggested are not correct, and this issue is only
> triggerable with root, by shooting yourself on the foot by misuing
> blktrace.
>
> If you want this on a git tree, you can get it from linux-next
> 20200401-blktrace-fix-uaf branch [2].
>
> Wider review, testing, and rants are appreciated.
>
> [0] https://bugzilla.kernel.org/show_bug.cgi?id=205713
> [1] https://nvd.nist.gov/vuln/detail/CVE-2019-19770
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20200401-blktrace-fix-uaf
>
> Luis Chamberlain (3):
> block: move main block debugfs initialization to its own file
> blktrace: fix debugfs use after free
> block: avoid deferral of blk_release_queue() work
>
> block/Makefile | 1 +
> block/blk-core.c | 9 +--------
> block/blk-debugfs.c | 27 +++++++++++++++++++++++++++
> block/blk-mq-debugfs.c | 5 -----
> block/blk-sysfs.c | 21 ++++++++-------------
> block/blk.h | 17 +++++++++++++++++
> include/linux/blktrace_api.h | 1 -
> kernel/trace/blktrace.c | 19 ++++++++-----------
> 8 files changed, 62 insertions(+), 38 deletions(-)
> create mode 100644 block/blk-debugfs.c

BTW, Yu Kuai posted one patch for this issue, looks that approach
is simpler:

https://lore.kernel.org/linux-block/20200324132315.22133-1-yukuai3@huawei.com/


Thanks,
Ming

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