ocfs2: fix uninit-value in ocfs2_get_block()

syzbot reported an uninit-value BUG:

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

This is because when ocfs2_extent_map_get_blocks() fails, p_blkno is
uninitialized.  So the error log will trigger the above uninit-value
access.

The error log is out-of-date since get_blocks() was removed long time ago.
And the error code will be logged in ocfs2_extent_map_get_blocks() once
ocfs2_get_cluster() fails, so fix this by only logging inode and block.

Link: https://syzkaller.appspot.com/bug?extid=9709e73bae885b05314b
Link: https://lkml.kernel.org/r/[email protected]
Fixes: ccd979b ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem")
Signed-off-by: Joseph Qi <[email protected]>
Reported-by: [email protected]
Tested-by: [email protected]
Cc: Heming Zhao <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Changwei Ge <[email protected]>
Cc: Gang He <[email protected]>
Cc: Jun Piao <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: josephhz

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;
 	}