linux-kernel - [syzbot] [f2fs?] KMSAN: uninit-value in __try_merge_extent

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Message-ID: <68532e0f.050a0220.216029.00aa.GAE@google.com>
Date: Wed, 18 Jun 2025 14:22:23 -0700
From: syzbot <syzbot+b8c1d60e95df65e827d4@...kaller.appspotmail.com>
To: chao@...nel.org, jaegeuk@...nel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [f2fs?] KMSAN: uninit-value in __try_merge_extent_node

Hello,

syzbot found the following issue on:

HEAD commit:    4774cfe3543a Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1219de0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=61539536677af51c
dashboard link: https://syzkaller.appspot.com/bug?extid=b8c1d60e95df65e827d4
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c5c5e2dcd9e4/disk-4774cfe3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ec9403177cd/vmlinux-4774cfe3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8c9c37a4fc0e/bzImage-4774cfe3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b8c1d60e95df65e827d4@...kaller.appspotmail.com

loop8: detected capacity change from 0 to 131072
F2FS-fs (loop8): Mounted with checkpoint version = 48b305e5
=====================================================
BUG: KMSAN: uninit-value in __is_extent_mergeable fs/f2fs/extent_cache.c:154 [inline]
BUG: KMSAN: uninit-value in __is_back_mergeable fs/f2fs/extent_cache.c:173 [inline]
BUG: KMSAN: uninit-value in __try_merge_extent_node+0x415/0x1600 fs/f2fs/extent_cache.c:546
 __is_extent_mergeable fs/f2fs/extent_cache.c:154 [inline]
 __is_back_mergeable fs/f2fs/extent_cache.c:173 [inline]
 __try_merge_extent_node+0x415/0x1600 fs/f2fs/extent_cache.c:546
 __update_extent_tree_range+0x1b53/0x2ae0 fs/f2fs/extent_cache.c:776
 __update_extent_cache+0x11cc/0x1420 fs/f2fs/extent_cache.c:950
 f2fs_update_read_extent_cache+0x20/0x30 fs/f2fs/extent_cache.c:1055
 f2fs_update_data_blkaddr+0x428/0x470 fs/f2fs/data.c:1142
 f2fs_outplace_write_data+0x1bf/0x250 fs/f2fs/segment.c:4011
 f2fs_do_write_data_page+0x2a11/0x3480 fs/f2fs/data.c:2752
 f2fs_write_single_data_page+0x15bf/0x29b0 fs/f2fs/data.c:2868
 f2fs_write_cache_pages fs/f2fs/data.c:3133 [inline]
 __f2fs_write_data_pages fs/f2fs/data.c:3282 [inline]
 f2fs_write_data_pages+0x2f66/0x5480 fs/f2fs/data.c:3309
 do_writepages+0x3f2/0x860 mm/page-writeback.c:2636
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x6f0/0x7d0 mm/filemap.c:794
 f2fs_do_sync_file+0x79b/0x31c0 fs/f2fs/file.c:278
 f2fs_sync_file+0x107/0x180 fs/f2fs/file.c:395
 vfs_fsync_range+0x1a1/0x240 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3027 [inline]
 f2fs_file_write_iter+0x3032/0x4650 fs/f2fs/file.c:5203
 do_iter_readv_writev+0x947/0xba0 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_pwritev fs/read_write.c:1153 [inline]
 __do_sys_pwritev2 fs/read_write.c:1211 [inline]
 __se_sys_pwritev2+0x22f/0x480 fs/read_write.c:1202
 __x64_sys_pwritev2+0xe4/0x150 fs/read_write.c:1202
 x64_sys_call+0x22b9/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:329
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable ei created at:
 f2fs_init_read_extent_tree+0xe7/0xf10 fs/f2fs/extent_cache.c:417
 do_read_inode fs/f2fs/inode.c:541 [inline]
 f2fs_iget+0x7a0e/0x8950 fs/f2fs/inode.c:589

CPU: 1 UID: 0 PID: 24362 Comm: syz.8.5691 Not tainted 6.16.0-rc1-syzkaller-00203-g4774cfe3543a #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


---
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