From: sashiko-bot@kernel.org
To: "Mohammad Mosafer" <mohsafer@gmail.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: [PATCH v2] usb: gadget: f_fs: fix use-after-free in ffs_closed() on umount
Date: Tue, 06 Oct 2026 22:00:03 +0000 [thread overview]
Message-ID: <sashiko-outbox-162472@kernel.org> (raw)
In-Reply-To: <20261006214940.158352-1-mohsafer@gmail.com>
> ffs_free_inst() releases the ffs_dev with ffs_release_dev() and only
> then re-acquires ffs_dev_lock to free it with _ffs_free_dev(). In
> between, the dev is still linked on the ffs_devices list while already
> marked unmounted, so a concurrent mount(2) of functionfs finds it by
> name in ffs_acquire_dev() and links a fresh ffs_data to the doomed dev
> (ffs_data->private_data = dev). _ffs_free_dev() then kfrees the dev,
> and when that mount is torn down, ffs_closed() dereferences the stale
> ffs->private_data:
>
> BUG: KASAN: slab-use-after-free in ffs_data_clear+0x438/0x530
> Write of size 1 at addr ffff88810594664a by task repro/116
> ffs_data_clear+0x438/0x530
> ffs_fs_kill_sb+0x7b/0x510
> deactivate_locked_super+0xa9/0x200
> cleanup_mnt+0x255/0x380
> [ ... ]
>
> Reported-by: syzbot+6227549bd2c8a1ec8ba0@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=6227549bd2c8a1ec8ba0
> Fixes: 5920cda627688c ("usb: gadget: FunctionFS: convert to new function interface with backward compatibility")
> Signed-off-by: Mohammad Mosafer <mohsafer@gmail.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261006214940.158352-1-mohsafer@gmail.com?part=1
prev parent reply other threads:[~2026-10-06 22:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-06 21:05 [PATCH] usb: gadget: f_fs: fix use-after-free in ffs_closed() on umount Mohammad Mosafer
2026-10-06 21:17 ` sashiko-bot
2026-10-06 21:49 ` [PATCH v2] " Mohammad Mosafer
2026-10-06 22:00 ` sashiko-bot [this message]
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