From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8041323CE; Tue, 3 Dec 2024 16:02:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733241762; cv=none; b=cXV07TTcslg7L5In05iroaYn0bmyd+OHOJnRVa7U7CQLSSvZeEQkPNEZVQKnBbrbU4VvC0+kFOn2a4AIXbLw82R7Eai2toglbPkjlaU2UUCo24lUEcfeRWNGyDwtx3tpSt/uF9pv6PMDrWn1cCeyoYQfg78VQTI/lwwFrGpj7bc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733241762; c=relaxed/simple; bh=Ww/xl3QLSn60Ic4rJ1dX8UI+k+JW2lqIy77FnVign3c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OlG28qP0NAIvqTjg763h48T/WqD8pLKC4Zxdcekr5FK7A4r3aSXiL9qjfEEVO1LqgUMqb5iTeNKbol7ISDhlhDXyclcA2c4EqzwICoT2iIh9Aj1guFsJB/ZOHyoyx4zz5ge0Q+BfW9qr+A6kosgCRIrQI4nWKz2xDyyiNMjxwy4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hwibIg+g; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hwibIg+g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70901C4CECF; Tue, 3 Dec 2024 16:02:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733241761; bh=Ww/xl3QLSn60Ic4rJ1dX8UI+k+JW2lqIy77FnVign3c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hwibIg+gwvkjGJsigVyZiH0wCROK1yxjHYewCUuVWY/+bLW1NrvsS5IvDo1oDP8HS gKOkXmuD4v96e9Xu62UDkEjmvuMfke/8zm7KEyvgGpqefEsx4SAlXpvWm2rfmrb/hF Pdzq5nyLATJLrPhGpzZs90DxOxtVJMTQnpQq+ErM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Long Li , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.12 507/826] f2fs: fix race in concurrent f2fs_stop_gc_thread Date: Tue, 3 Dec 2024 15:43:54 +0100 Message-ID: <20241203144803.533570957@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241203144743.428732212@linuxfoundation.org> References: <20241203144743.428732212@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Long Li [ Upstream commit 7b0033dbc48340a1c1c3f12448ba17d6587ca092 ] In my test case, concurrent calls to f2fs shutdown report the following stack trace: Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 Call Trace: ? show_regs+0x8b/0xa0 ? __die_body+0x26/0xa0 ? die_addr+0x54/0x90 ? exc_general_protection+0x24b/0x5c0 ? asm_exc_general_protection+0x26/0x30 ? kthread_stop+0x46/0x390 f2fs_stop_gc_thread+0x6c/0x110 f2fs_do_shutdown+0x309/0x3a0 f2fs_ioc_shutdown+0x150/0x1c0 __f2fs_ioctl+0xffd/0x2ac0 f2fs_ioctl+0x76/0xe0 vfs_ioctl+0x23/0x60 __x64_sys_ioctl+0xce/0xf0 x64_sys_call+0x2b1b/0x4540 do_syscall_64+0xa7/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e The root cause is a race condition in f2fs_stop_gc_thread() called from different f2fs shutdown paths: [CPU0] [CPU1] ---------------------- ----------------------- f2fs_stop_gc_thread f2fs_stop_gc_thread gc_th = sbi->gc_thread gc_th = sbi->gc_thread kfree(gc_th) sbi->gc_thread = NULL < gc_th != NULL > kthread_stop(gc_th->f2fs_gc_task) //UAF The commit c7f114d864ac ("f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread()") attempted to fix this issue by using a read semaphore to prevent races between shutdown and remount threads, but it fails to prevent all race conditions. Fix it by converting to write lock of s_umount in f2fs_do_shutdown(). Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") Signed-off-by: Long Li Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/file.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index adc7d64a6f47d..b96403ab7a925 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2343,9 +2343,12 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, if (readonly) goto out; - /* grab sb->s_umount to avoid racing w/ remount() */ + /* + * grab sb->s_umount to avoid racing w/ remount() and other shutdown + * paths. + */ if (need_lock) - down_read(&sbi->sb->s_umount); + down_write(&sbi->sb->s_umount); f2fs_stop_gc_thread(sbi); f2fs_stop_discard_thread(sbi); @@ -2354,7 +2357,7 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, clear_opt(sbi, DISCARD); if (need_lock) - up_read(&sbi->sb->s_umount); + up_write(&sbi->sb->s_umount); f2fs_update_time(sbi, REQ_TIME); out: -- 2.43.0