ext4: xattr: fix null pointer deref in ext4_raw_inode()

ext4: xattr: fix null pointer deref in ext4_raw_inode()

If ext4_get_inode_loc() fails (e.g. if it returns -EFSCORRUPTED),
iloc.bh will remain set to NULL. Since ext4_xattr_inode_dec_ref_all()
lacks error checking, this will lead to a null pointer dereference
in ext4_raw_inode(), called right after ext4_get_inode_loc().

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: c8e008b60492 ("ext4: ignore xattrs past end")
Cc: stable@kernel.org
Signed-off-by: Karina Yankevich <k.yankevich@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Message-ID: <20251022093253.3546296-1-k.yankevich@omp.ru>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>