Commit b6718969 authored Mar 13, 2024 by Ryusuke Konishi Committed by Greg Kroah-Hartman Apr 13, 2024

nilfs2: fix failure to detect DAT corruption in btree and direct mappings

[ Upstream commit f2f26b4a84a0ef41791bd2d70861c8eac748f4ba ]

Patch series "nilfs2: fix kernel bug at submit_bh_wbc()".

This resolves a kernel BUG reported by syzbot. Since there are two
flaws involved, I've made each one a separate patch.

The first patch alone resolves the syzbot-reported bug, but I think
both fixes should be sent to stable, so I've tagged them as such.

This patch (of 2):

Syzbot has reported a kernel bug in submit_bh_wbc() when writing file data
to a nilfs2 file system whose metadata is corrupted.

There are two flaws involved in this issue.

The first flaw is that when nilfs_get_block() locates a data block using
btree or direct mapping, if the disk address translation routine
nilfs_dat_translate() fails with internal code -ENOENT due to DAT metadata
corruption, it can be passed back to nilfs_get_block(). This causes
nilfs_get_block() to misidentify an existing block as non-existent,
causing both data block lookup and insertion to fail inconsistently.

The second flaw is that nilfs_get_block() returns a successful status in
this inconsistent state. This causes the caller __block_write_begin_int()
or others to request a read even though the buffer is not mapped,
resulting in a BUG_ON check for the BH_Mapped flag in submit_bh_wbc()
failing.

This fixes the first issue by changing the return value to code -EINVAL
when a conversion using DAT fails with code -ENOENT, avoiding the
conflicting condition that leads to the kernel bug described above. Here,
code -EINVAL indicates that metadata corruption was detected during the
block lookup, which will be properly handled as a file system error and
converted to -EIO when passing through the nilfs2 bmap layer.

Link: https://lkml.kernel.org/r/20240313105827.5296-1-konishi.ryusuke@gmail.com
Link: https://lkml.kernel.org/r/20240313105827.5296-2-konishi.ryusuke@gmail.com

Fixes: c3a7abf0 ("nilfs2: support contiguous lookup of blocks")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: <syzbot+cfed5b56649bddf80d6e@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=cfed5b56649bddf80d6e

Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 6e7044f1

fs/nilfs2/btree.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -724,7 +724,7 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
		dat = nilfs_bmap_get_dat(btree);
		ret = nilfs_dat_translate(dat, ptr, &blocknr);
		if (ret < 0)
		goto out;
		goto dat_error;
		ptr = blocknr;
		}
		cnt = 1;
		@@ -743,7 +743,7 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
		if (dat) {
		ret = nilfs_dat_translate(dat, ptr2, &blocknr);
		if (ret < 0)
		goto out;
		goto dat_error;
		ptr2 = blocknr;
		}
		if (ptr2 != ptr + cnt \|\| ++cnt == maxblocks)
		@@ -782,6 +782,11 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
		out:
		nilfs_btree_free_path(path);
		return ret;

		dat_error:
		if (ret == -ENOENT)
		ret = -EINVAL; /* Notify bmap layer of metadata corruption */
		goto out;
		}

		static void nilfs_btree_promote_key(struct nilfs_bmap *btree,

fs/nilfs2/direct.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -66,7 +66,7 @@ static int nilfs_direct_lookup_contig(const struct nilfs_bmap *direct,
		dat = nilfs_bmap_get_dat(direct);
		ret = nilfs_dat_translate(dat, ptr, &blocknr);
		if (ret < 0)
		return ret;
		goto dat_error;
		ptr = blocknr;
		}

		@@ -79,7 +79,7 @@ static int nilfs_direct_lookup_contig(const struct nilfs_bmap *direct,
		if (dat) {
		ret = nilfs_dat_translate(dat, ptr2, &blocknr);
		if (ret < 0)
		return ret;
		goto dat_error;
		ptr2 = blocknr;
		}
		if (ptr2 != ptr + cnt)
		@@ -87,6 +87,11 @@ static int nilfs_direct_lookup_contig(const struct nilfs_bmap *direct,
		}
		*ptrp = ptr;
		return cnt;

		dat_error:
		if (ret == -ENOENT)
		ret = -EINVAL; /* Notify bmap layer of metadata corruption */
		return ret;
		}

		static __u64