linux-kernel - [PATCH v8 0/2] firmware_loader: fix uaf in firmware_fallback

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Date:   Wed, 28 Jul 2021 14:21:05 +0530
From:   Anirudh Rayabharam <mail@...rudhrb.com>
To:     mcgrof@...nel.org, gregkh@...uxfoundation.org, rafael@...nel.org,
        skhan@...uxfoundation.org
Cc:     Anirudh Rayabharam <mail@...rudhrb.com>,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH v8 0/2] firmware_loader: fix uaf in firmware_fallback_sysfs

This series fixes the use after free in firmware_fallback_sysfs reported by
syzbot at: 
https://syzkaller.appspot.com/bug?extid=de271708674e2093097b

The first patch gets rid of the -EAGAIN return since it doesn't make
sense (see patch description for more info). The second patch goes on to
actually fix the use after free issue.

Changes in v8:
1. Added/fixed some comments as suggested by Shuah

Changes in v7:
1. Don't move the error handling code from fw_load_sysfs_fallback
   to fw_sysfs_wait_timeout to simplify the patch. Also, the move
   is unnecessary.

2. Fix the commit log for patch 1 as per Luis' suggestions.

Changes in v6:
1. v5 didn't actually remove -EAGAIN. So, fixed that.

Changes in v5:
1. Split the patch into two patches as discussed here:
   https://lore.kernel.org/lkml/20210715232105.am4wsxfclj2ufjdw@garbanzo/

Changes in v4:
Documented the reasons behind the error codes returned from
fw_sysfs_wait_timeout() as suggested by Luis Chamberlain.

Changes in v3:
Modified the patch to incorporate suggestions by Luis Chamberlain in
order to fix the root cause instead of applying a "band-aid" kind of
fix.
https://lore.kernel.org/lkml/20210403013143.GV4332@42.do-not-panic.com/

Changes in v2:
1. Fixed 1 error and 1 warning (in the commit message) reported by
checkpatch.pl. The error was regarding the format for referring to
another commit "commit <sha> ("oneline")". The warning was for line
longer than 75 chars.

Anirudh Rayabharam (2):
  firmware_loader: use -ETIMEDOUT instead of -EAGAIN in
    fw_load_sysfs_fallback
  firmware_loader: fix use-after-free in firmware_fallback_sysfs

 drivers/base/firmware_loader/fallback.c | 14 ++++++++------
 drivers/base/firmware_loader/firmware.h | 10 +++++++++-
 drivers/base/firmware_loader/main.c     |  2 ++
 3 files changed, 19 insertions(+), 7 deletions(-)

-- 
2.26.2