The patch titled
Subject: nilfs2: fix failure to detect DAT corruption in btree and direct mappings
has been added to the -mm mm-nonmm-unstable branch. Its filename is
nilfs2-fix-failure-to-detect-dat-corruption-in-btree-and-direct-mappings.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-failure-to-detect-dat-corruption-in-btree-and-direct-mappings.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Subject: nilfs2: fix failure to detect DAT corruption in btree and direct mappings
Date: Wed, 13 Mar 2024 19:58:26 +0900
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@xxxxxxxxx
Link: https://lkml.kernel.org/r/20240313105827.5296-2-konishi.ryusuke@xxxxxxxxx
Fixes: c3a7abf06ce7 ("nilfs2: support contiguous lookup of blocks")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+cfed5b56649bddf80d6e@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=cfed5b56649bddf80d6e
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/btree.c | 9 +++++++--
fs/nilfs2/direct.c | 9 +++++++--
2 files changed, 14 insertions(+), 4 deletions(-)
--- a/fs/nilfs2/btree.c~nilfs2-fix-failure-to-detect-dat-corruption-in-btree-and-direct-mappings
+++ a/fs/nilfs2/btree.c
@@ -724,7 +724,7 @@ static int nilfs_btree_lookup_contig(con
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(con
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)
@@ -781,6 +781,11 @@ static int nilfs_btree_lookup_contig(con
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,
--- a/fs/nilfs2/direct.c~nilfs2-fix-failure-to-detect-dat-corruption-in-btree-and-direct-mappings
+++ a/fs/nilfs2/direct.c
@@ -66,7 +66,7 @@ static int nilfs_direct_lookup_contig(co
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(co
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(co
}
*ptrp = ptr;
return cnt;
+
+ dat_error:
+ if (ret == -ENOENT)
+ ret = -EINVAL; /* Notify bmap layer of metadata corruption */
+ return ret;
}
static __u64
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-failure-to-detect-dat-corruption-in-btree-and-direct-mappings.patch
nilfs2-prevent-kernel-bug-at-submit_bh_wbc.patch
