The patch titled
Subject: nilfs2: fix potential null-ptr-deref in nilfs_btree_insert()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
nilfs2-fix-potential-null-ptr-deref-in-nilfs_btree_insert.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-potential-null-ptr-deref-in-nilfs_btree_insert.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 potential null-ptr-deref in nilfs_btree_insert()
Date: Wed, 4 Sep 2024 17:13:07 +0900
Patch series "nilfs2: fix potential issues with empty b-tree nodes".
This series addresses three potential issues with empty b-tree nodes that
can occur with corrupted filesystem images, including one recently
discovered by syzbot.
This patch (of 3):
If a b-tree is broken on the device, and the b-tree height is greater than
2 (the level of the root node is greater than 1) even if the number of
child nodes of the b-tree root is 0, a NULL pointer dereference occurs in
nilfs_btree_prepare_insert(), which is called from nilfs_btree_insert().
This is because, when the number of child nodes of the b-tree root is 0,
nilfs_btree_do_lookup() does not set the block buffer head in any of
path[x].bp_bh, leaving it as the initial value of NULL, but if the level
of the b-tree root node is greater than 1, nilfs_btree_get_nonroot_node(),
which accesses the buffer memory of path[x].bp_bh, is called.
Fix this issue by adding a check to nilfs_btree_root_broken(), which
performs sanity checks when reading the root node from the device, to
detect this inconsistency.
Thanks to Lizhi Xu for trying to solve the bug and clarifying the cause
early on.
Link: https://lkml.kernel.org/r/20240904081401.16682-1-konishi.ryusuke@xxxxxxxxx
Link: https://lkml.kernel.org/r/20240902084101.138971-1-lizhi.xu@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240904081401.16682-2-konishi.ryusuke@xxxxxxxxx
Fixes: 17c76b0104e4 ("nilfs2: B-tree based block mapping")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+9bff4c7b992038a7409f@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=9bff4c7b992038a7409f
Cc: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/btree.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/nilfs2/btree.c~nilfs2-fix-potential-null-ptr-deref-in-nilfs_btree_insert
+++ a/fs/nilfs2/btree.c
@@ -381,7 +381,8 @@ static int nilfs_btree_root_broken(const
if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
level >= NILFS_BTREE_LEVEL_MAX ||
nchildren < 0 ||
- nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
+ nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX ||
+ (nchildren == 0 && level > NILFS_BTREE_LEVEL_NODE_MIN))) {
nilfs_crit(inode->i_sb,
"bad btree root (ino=%lu): level = %d, flags = 0x%x, nchildren = %d",
inode->i_ino, level, flags, nchildren);
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-potential-null-ptr-deref-in-nilfs_btree_insert.patch
nilfs2-determine-empty-node-blocks-as-corrupted.patch
nilfs2-fix-potential-oob-read-in-nilfs_btree_check_delete.patch
