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Subject: [PATCH] ext4: handle corrupted xattr entries in ext4_xattr_move_to_block
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

During inode expansion, ext4_xattr_move_to_block() can encounter corrupted
xattr entries where e_value_size is zero but e_value_inum is non-zero,
indicating the entry claims to store its value in a separate inode but
has no actual value. This leads to a WARNING in ext4_xattr_block_set()
when it hits WARN_ON_ONCE(!i->value_len).

Add validation in ext4_xattr_move_to_block() to detect this corruption
pattern early and return -EFSCORRUPTED instead of allowing the invalid
data to propagate and trigger warnings.

Reported-by: syzbot+4c9d23743a2409b80293@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=4c9d23743a2409b80293
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/ext4/xattr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 5a6fe1513fd2..cbe06d7e3bb6 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2607,7 +2607,10 @@ static int ext4_xattr_move_to_block(handle_t *handle, struct inode *inode,
 	struct ext4_xattr_ibody_header *header = IHDR(inode, raw_inode);
 	int needs_kvfree = 0;
 	int error;
-
+	if (value_size == 0 && entry->e_value_inum != 0) {
+	    error = -EFSCORRUPTED;
+	goto out;
+	}
 	is = kzalloc(sizeof(struct ext4_xattr_ibody_find), GFP_NOFS);
 	bs = kzalloc(sizeof(struct ext4_xattr_block_find), GFP_NOFS);
 	b_entry_name = kmalloc(entry->e_name_len + 1, GFP_NOFS);
-- 
2.43.0