This is a note to let you know that I've just added the patch titled
nilfs2: fix potential null-ptr-deref in nilfs_btree_insert()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-fix-potential-null-ptr-deref-in-nilfs_btree_i.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 34f6acefc71a2d14e2a1e362c1528ff58ab53a25
Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Date: Wed Sep 4 17:13:07 2024 +0900
nilfs2: fix potential null-ptr-deref in nilfs_btree_insert()
[ Upstream commit 9403001ad65ae4f4c5de368bdda3a0636b51d51a ]
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>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index a426e4e2acdac..c2aca9cd78644 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -381,7 +381,8 @@ static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
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);
