Re: NULL pointer dereference in ext4_ext_remove_space on 3.5.1
From: Theodore Ts'o <tytso@mit.edu>
Date: 2012-08-16 02:47:06
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lkml
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
On Wed, Aug 15, 2012 at 09:33:29PM +0300, Marti Raudsepp wrote:
I was moving and deleting some files between two of my ext4 partitions when it suddenly crashed and dropped me into an kernel oops screen (below). I'm using ext4 on kernel 3.5.1 (Arch Linux).
BUG: unable to handle kernel NULL pointer dereference at 000...00028 IP: [...] ext4_ext_remove_space+0xaa4/0xef0 [ext4]
Someone else has reported a similar crash, but we don't yet have enough information to narrow it down quite yet. If you could try applying the following debugging patch, and then try to reproduce the failure, it would be really helpful. Thanks!! - Ted
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 769151d..3394d52 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c@@ -2432,6 +2432,10 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode, /* the header must be checked already in ext4_ext_remove_space() */ ext_debug("truncate since %u in leaf to %u\n", start, end); + if (!path[depth].p_hdr && !path[depth].p_bh) { + EXT4_ERROR_INODE(inode, "depth %d", depth); + BUG_ON(1); + } if (!path[depth].p_hdr) path[depth].p_hdr = ext_block_hdr(path[depth].p_bh); eh = path[depth].p_hdr;
@@ -2730,6 +2734,10 @@ cont: /* this is index block */ if (!path[i].p_hdr) { ext_debug("initialize header\n"); + if (!path[i].p_hdr && !path[i].p_bh) { + EXT4_ERROR_INODE(inode, "i=%d", i); + BUG_ON(1); + } path[i].p_hdr = ext_block_hdr(path[i].p_bh); }