From nobody Thu Dec 18 09:24:42 2025 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 701BC1EA7E6 for ; Mon, 24 Feb 2025 10:29:28 +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=1740392968; cv=none; b=ADRnnrQYfWFYqHD/iIPrLaVAwz32gz7A1eqBdaYlqt+9WPYQNmoM0Noq9kwZDrcLaMlaQeSHHZwkHrk1hVigkUDD5H01JM0r41zitIt0KdNQ1uK4nWFn8qJ9XTPCAplhNJ/5hzQqC0jJihIm2DeogF7wYFO0isQEyBNrydQZgrs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740392968; c=relaxed/simple; bh=dWEGzYt4wM4ufHLVVrN6xRzW2jMG5XwLK79Wlm0T60M=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=JK30Gxrqhw5BexdxFX7dk0qYgJ2cAsMP7M01LoxofEvMxsHrlVueHR76YUK9WGv+r6STeOcc+tnnPNrOWT80iOayeOAxQSst5nZKezVlz0rdhtL3K02inLsgdsNJamVjUt0VB7Pt2dCmKnNG2kdw+nc5biEYEDVtfXREHDXByc8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NAUxquax; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NAUxquax" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFEAAC4CED6; Mon, 24 Feb 2025 10:29:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740392967; bh=dWEGzYt4wM4ufHLVVrN6xRzW2jMG5XwLK79Wlm0T60M=; h=From:To:Cc:Subject:Date:From; b=NAUxquaxkaLTf1W3DN1oNtcJdmMex0f1RFv+yq7kKNqcJzQz7seFScQhBXCJEY2tY BfotNacrulqKBUk35EyJ1hPE/SKjKtuVHP1YbjaVGvzZAR81BF9FCIPTTnXWkv+0mY BnXTvPo3ZEiOo6oO3JzaFB/aED0KbDGelSWXZluV2jOss/M7NAE+hTUTnRLQo6fbxk henFwhsBaPVYW83+AYCs/gWajDyoRE4RZf54K14nBmtFio0hStTkjpzxcgUUgzsi1J ruICIjcKEsoRqYxU2RH8IMRQ5PdZaFTYRg+yhjGVrSyNDOzh6QjwrnPt0aixQuiiGX tmyje3REYnqww== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , syzbot+b6b347b7a4ea1b2e29b6@syzkaller.appspotmail.com Subject: [PATCH v2] f2fs: fix to avoid accessing uninitialized curseg Date: Mon, 24 Feb 2025 18:29:23 +0800 Message-ID: <20250224102923.93758-1-chao@kernel.org> X-Mailer: git-send-email 2.48.1.601.g30ceb7b040-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" syzbot reports a f2fs bug as below: F2FS-fs (loop3): Stopped filesystem due to reason: 7 kworker/u8:7: attempt to access beyond end of device BUG: unable to handle page fault for address: ffffed1604ea3dfa RIP: 0010:get_ckpt_valid_blocks fs/f2fs/segment.h:361 [inline] RIP: 0010:has_curseg_enough_space fs/f2fs/segment.h:570 [inline] RIP: 0010:__get_secs_required fs/f2fs/segment.h:620 [inline] RIP: 0010:has_not_enough_free_secs fs/f2fs/segment.h:633 [inline] RIP: 0010:has_enough_free_secs+0x575/0x1660 fs/f2fs/segment.h:649 f2fs_is_checkpoint_ready fs/f2fs/segment.h:671 [inline] f2fs_write_inode+0x425/0x540 fs/f2fs/inode.c:791 write_inode fs/fs-writeback.c:1525 [inline] __writeback_single_inode+0x708/0x10d0 fs/fs-writeback.c:1745 writeback_sb_inodes+0x820/0x1360 fs/fs-writeback.c:1976 wb_writeback+0x413/0xb80 fs/fs-writeback.c:2156 wb_do_writeback fs/fs-writeback.c:2303 [inline] wb_workfn+0x410/0x1080 fs/fs-writeback.c:2343 process_one_work kernel/workqueue.c:3236 [inline] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317 worker_thread+0x870/0xd30 kernel/workqueue.c:3398 kthread+0x7a9/0x920 kernel/kthread.c:464 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Commit 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT") allows to trigger no free segment fault in allocator, then it will update curseg->segno to NULL_SEGNO, though, CP_ERROR_FLAG has been set, f2fs_write_inode() missed to check the flag, and access invalid curseg->segno directly in below call path, then resulting in panic: - f2fs_write_inode - f2fs_is_checkpoint_ready - has_enough_free_secs - has_not_enough_free_secs - __get_secs_required - has_curseg_enough_space - get_ckpt_valid_blocks : access invalid curseg->segno To avoid this issue, let's: - check CP_ERROR_FLAG flag in prior to f2fs_is_checkpoint_ready() in f2fs_write_inode(). - in has_curseg_enough_space(), save curseg->segno into a temp variable, and verify its validation before use. Fixes: 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT") Reported-by: syzbot+b6b347b7a4ea1b2e29b6@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/67973c2b.050a0220.11b1bb.0089.GAE@googl= e.com Signed-off-by: Chao Yu --- v2: - get rid of potential blocking on curseg_mutex fs/f2fs/inode.c | 7 +++++++ fs/f2fs/segment.h | 9 ++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c index d6ad7810df69..6aec752ac098 100644 --- a/fs/f2fs/inode.c +++ b/fs/f2fs/inode.c @@ -793,6 +793,13 @@ int f2fs_write_inode(struct inode *inode, struct write= back_control *wbc) !is_inode_flag_set(inode, FI_DIRTY_INODE)) return 0; =20 + /* + * no need to update inode page, ultimately f2fs_evict_inode() will + * clear dirty status of inode. + */ + if (f2fs_cp_error(sbi)) + return -EIO; + if (!f2fs_is_checkpoint_ready(sbi)) { f2fs_mark_inode_dirty_sync(inode, true); return -ENOSPC; diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h index 943be4f1d6d2..0465dc00b349 100644 --- a/fs/f2fs/segment.h +++ b/fs/f2fs/segment.h @@ -559,13 +559,16 @@ static inline bool has_curseg_enough_space(struct f2f= s_sb_info *sbi, unsigned int node_blocks, unsigned int data_blocks, unsigned int dent_blocks) { - unsigned int segno, left_blocks, blocks; int i; =20 /* check current data/node sections in the worst case. */ for (i =3D CURSEG_HOT_DATA; i < NR_PERSISTENT_LOG; i++) { segno =3D CURSEG_I(sbi, i)->segno; + + if (unlikely(segno =3D=3D NULL_SEGNO)) + return false; + left_blocks =3D CAP_BLKS_PER_SEC(sbi) - get_ckpt_valid_blocks(sbi, segno, true); =20 @@ -576,6 +579,10 @@ static inline bool has_curseg_enough_space(struct f2fs= _sb_info *sbi, =20 /* check current data section for dentry blocks. */ segno =3D CURSEG_I(sbi, CURSEG_HOT_DATA)->segno; + + if (unlikely(segno =3D=3D NULL_SEGNO)) + return false; + left_blocks =3D CAP_BLKS_PER_SEC(sbi) - get_ckpt_valid_blocks(sbi, segno, true); if (dent_blocks > left_blocks) --=20 2.48.1.601.g30ceb7b040-goog