Re: [syzbot] [ocfs2?] KMSAN: uninit-value in ocfs2_get_block

[Joseph Qi <joseph.qi@linux.alibaba.com>]

This blames p_blkno is uninitialized when ocfs2_extent_map_get_blocks()
fails.

#syz test

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 1fea43c33b6b..db72b3e924b3 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -156,9 +156,8 @@ int ocfs2_get_block(struct inode *inode, sector_t iblock,
 	err = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno, &count,
 					  &ext_flags);
 	if (err) {
-		mlog(ML_ERROR, "Error %d from get_blocks(0x%p, %llu, 1, "
-		     "%llu, NULL)\n", err, inode, (unsigned long long)iblock,
-		     (unsigned long long)p_blkno);
+		mlog(ML_ERROR, "get_blocks() failed, inode: 0x%p, "
+		     "block: %llu\n", inode, (unsigned long long)iblock);
 		goto bail;
 	}


On 9/25/24 9:28 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    baeb9a7d8b60 Merge tag 'sched-rt-2024-09-17' of git://git...
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=172af607980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=acaa65be5f19fc5a
> dashboard link: https://syzkaller.appspot.com/bug?extid=9709e73bae885b05314b
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=161e2ca9980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=151bff00580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/cac89ddb3388/disk-baeb9a7d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ddec90b149ab/vmlinux-baeb9a7d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/f8db8244cc07/bzImage-baeb9a7d.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/25ed405f5727/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9709e73bae885b05314b@syzkaller.appspotmail.com
> 
> OCFS2: ERROR (device loop0): int __ocfs2_find_path(struct ocfs2_caching_info *, struct ocfs2_extent_list *, u32, path_insert_t *, void *): Owner 17 has empty extent list at depth 312
> On-disk corruption discovered. Please run fsck.ocfs2 once the filesystem is unmounted.
> OCFS2: Returning error to the calling process.
> (syz-executor337,5180,0):ocfs2_find_leaf:1940 ERROR: status = -30
> (syz-executor337,5180,0):ocfs2_get_clusters_nocache:421 ERROR: status = -30
> (syz-executor337,5180,0):ocfs2_get_clusters:624 ERROR: status = -30
> (syz-executor337,5180,0):ocfs2_extent_map_get_blocks:671 ERROR: status = -30
> =====================================================
> BUG: KMSAN: uninit-value in ocfs2_get_block+0xed2/0x2710 fs/ocfs2/aops.c:159
>  ocfs2_get_block+0xed2/0x2710 fs/ocfs2/aops.c:159
>  do_mpage_readpage+0xc45/0x2780 fs/mpage.c:225
>  mpage_readahead+0x43f/0x840 fs/mpage.c:374
>  ocfs2_readahead+0x269/0x320 fs/ocfs2/aops.c:381
>  read_pages+0x193/0x1110 mm/readahead.c:160
>  page_cache_ra_unbounded+0x901/0x9f0 mm/readahead.c:273
>  do_page_cache_ra mm/readahead.c:303 [inline]
>  force_page_cache_ra+0x3b1/0x4b0 mm/readahead.c:332
>  force_page_cache_readahead mm/internal.h:347 [inline]
>  generic_fadvise+0x6b0/0xa90 mm/fadvise.c:106
>  vfs_fadvise mm/fadvise.c:185 [inline]
>  ksys_fadvise64_64 mm/fadvise.c:199 [inline]
>  __do_sys_fadvise64 mm/fadvise.c:214 [inline]
>  __se_sys_fadvise64 mm/fadvise.c:212 [inline]
>  __x64_sys_fadvise64+0x1fb/0x3a0 mm/fadvise.c:212
>  x64_sys_call+0xe11/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:222
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Local variable p_blkno created at:
>  ocfs2_get_block+0xc7/0x2710 fs/ocfs2/aops.c:140
>  do_mpage_readpage+0xc45/0x2780 fs/mpage.c:225
> 
> CPU: 0 UID: 0 PID: 5180 Comm: syz-executor337 Not tainted 6.11.0-syzkaller-07341-gbaeb9a7d8b60 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
> =====================================================
> 
> 
> ---
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> 
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