[PATCH 1/3] ocfs2: handle invalid dinode in reserve_suballoc_bits

[ZhengYuan Huang <gality369@gmail.com>]

[BUG]
A crafted filesystem can feed an invalid dinode into
ocfs2_reserve_suballoc_bits() and trip:

kernel BUG at fs/ocfs2/suballoc.c:806!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:ocfs2_reserve_suballoc_bits+0xccd/0x3e00 fs/ocfs2/suballoc.c:806
Code: c0fe488b 9d58ffff ff4885db 740de8fa
Call Trace:
 <TASK>
 ocfs2_reserve_cluster_bitmap_bits+0xe5/0x1c0 fs/ocfs2/suballoc.c:1134
 ocfs2_local_alloc_reserve_for_window fs/ocfs2/localalloc.c:1108 [inline]
 ocfs2_local_alloc_slide_window+0x2cb/0x1570 fs/ocfs2/localalloc.c:1244
 ocfs2_reserve_local_alloc_bits+0x654/0xa10 fs/ocfs2/localalloc.c:669
 ocfs2_reserve_clusters_with_limit+0x785/0xe40 fs/ocfs2/suballoc.c:1168
 ocfs2_reserve_clusters fs/ocfs2/suballoc.c:1229 [inline]
 ocfs2_lock_allocators+0x319/0x520 fs/ocfs2/suballoc.c:2772
 ocfs2_write_begin_nolock+0x256a/0x5f30 fs/ocfs2/aops.c:1719
 ocfs2_write_begin+0x1b6/0x2e0 fs/ocfs2/aops.c:1884
 generic_perform_write+0x409/0x8c0 mm/filemap.c:4255
 __generic_file_write_iter+0x1bb/0x200 mm/filemap.c:4372
 ocfs2_file_write_iter+0xa87/0x1e10 fs/ocfs2/file.c:2469
 do_iter_readv_writev+0x61d/0x850 fs/read_write.c:827
 vfs_writev+0x323/0xca0 fs/read_write.c:1057
 do_pwritev+0x193/0x250 fs/read_write.c:1153
 __do_sys_pwritev2 fs/read_write.c:1211 [inline]
 __se_sys_pwritev2 fs/read_write.c:1202 [inline]
 __x64_sys_pwritev2+0xe8/0x160 fs/read_write.c:1202
 ...

[CAUSE]
ocfs2_reserve_suballoc_bits() assumes ocfs2_inode_lock() always returns
an already validated dinode buffer. commit 10995aa2451a ("ocfs2: Morph
the haphazard OCFS2_IS_VALID_DINODE() checks.") replaced the old
corruption handling with BUG_ON() under that assumption. However,
JBD-managed buffers can still bypass inode validation in the read path,
so corrupted dinode data can reach this function.

[FIX]
Treat an invalid dinode as filesystem corruption and return through the
existing bail-out path instead of BUG()ing. This matches the nearby
OCFS2_CHAIN_FL handling and keeps allocator cleanup unchanged.

Fixes: 10995aa2451a ("ocfs2: Morph the haphazard OCFS2_IS_VALID_DINODE() checks.")
Signed-off-by: ZhengYuan Huang <gality369@gmail.com>
 fs/ocfs2/suballoc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index 6ac4dcd54588..12ac2bb3f10b 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -801,9 +801,13 @@ static int ocfs2_reserve_suballoc_bits(struct ocfs2_super *osb,
 
 	fe = (struct ocfs2_dinode *) bh->b_data;
 
-	/* The bh was validated by the inode read inside
-	 * ocfs2_inode_lock().  Any corruption is a code bug. */
-	BUG_ON(!OCFS2_IS_VALID_DINODE(fe));
+	/* JBD-managed buffers can bypass inode validation. */
+	if (!OCFS2_IS_VALID_DINODE(fe)) {
+		status = ocfs2_error(alloc_inode->i_sb,
+				     "Invalid dinode #%llu\n",
+				     (unsigned long long)OCFS2_I(alloc_inode)->ip_blkno);
+		goto bail;
+	}
 
 	if (!(fe->i_flags & cpu_to_le32(OCFS2_CHAIN_FL))) {
 		status = ocfs2_error(alloc_inode->i_sb,
-- 
2.43.0