Patchwork e2fsprogs: allow 0-length xattr values in e2fsck

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Submitter Eric Sandeen
Date April 7, 2013, 6:42 p.m.
Message ID <5161BE0A.5070003@redhat.com>
Download mbox | patch
Permalink /patch/234516/
State Accepted
Headers show

Comments

Eric Sandeen - April 7, 2013, 6:42 p.m.
e2fsck thinks that this:

# touch mnt/testfile1
# setfattr -n "user.test" mnt/testfile1

results in a filesystem with corruption:

Pass 1: Checking inodes, blocks, and sizes
Extended attribute in inode 12 has a value size (0) which is invalid
Clear? yes

but as far as I can tell, there is absolutely nothing wrong with
a 0-length value on an extended attribute.  Just remove the check.

Reported-by: David Shaw <dshaw@jabberwocky.com>
Reported-by: Harald Reindl <h.reindl@thelounge.net>
Addresses-Red-Hat-Bugzilla: #557959
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

Strange that this has been in e2fsck since 2005; apologies to 
David in particular for not addressing the bug he filed much sooner,
I had assumed that this was some strange corruption, not a simple
logic error / change.


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Eric Sandeen - April 12, 2013, 5:02 p.m.
On 4/7/13 1:42 PM, Eric Sandeen wrote:
> e2fsck thinks that this:
> 
> # touch mnt/testfile1
> # setfattr -n "user.test" mnt/testfile1
> 
> results in a filesystem with corruption:
> 
> Pass 1: Checking inodes, blocks, and sizes
> Extended attribute in inode 12 has a value size (0) which is invalid
> Clear? yes
> 
> but as far as I can tell, there is absolutely nothing wrong with
> a 0-length value on an extended attribute.  Just remove the check.
> 
> Reported-by: David Shaw <dshaw@jabberwocky.com>
> Reported-by: Harald Reindl <h.reindl@thelounge.net>
> Addresses-Red-Hat-Bugzilla: #557959
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Ted, just a ping on this.  I know there's been a lot going on,so
wasn't sure if you missed it, or if it's just saved for later.

Thanks,
-Eric

> ---
> 
> Strange that this has been in e2fsck since 2005; apologies to 
> David in particular for not addressing the bug he filed much sooner,
> I had assumed that this was some strange corruption, not a simple
> logic error / change.
> 
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index a20b57b..94df36d 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -307,7 +307,7 @@ static void check_ea_in_inode(e2fsck_t ctx, struct problem_context *pctx)
>  		remain -= EXT2_EXT_ATTR_SIZE(entry->e_name_len);
>  
>  		/* check value size */
> -		if (entry->e_value_size == 0 || entry->e_value_size > remain) {
> +		if (entry->e_value_size > remain) {
>  			pctx->num = entry->e_value_size;
>  			problem = PR_1_ATTR_VALUE_SIZE;
>  			goto fix;
> 
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Theodore Ts'o - April 25, 2013, 4:20 a.m.
On Sun, Apr 07, 2013 at 01:42:18PM -0500, Eric Sandeen wrote:
> e2fsck thinks that this:
> 
> # touch mnt/testfile1
> # setfattr -n "user.test" mnt/testfile1
> 
> results in a filesystem with corruption:
> 
> Pass 1: Checking inodes, blocks, and sizes
> Extended attribute in inode 12 has a value size (0) which is invalid
> Clear? yes
> 
> but as far as I can tell, there is absolutely nothing wrong with
> a 0-length value on an extended attribute.  Just remove the check.
> 
> Reported-by: David Shaw <dshaw@jabberwocky.com>
> Reported-by: Harald Reindl <h.reindl@thelounge.net>
> Addresses-Red-Hat-Bugzilla: #557959
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Thanks, applied.

It turns out that 0-length values applied for xattrs stored in
external xattr blocks.  0-length xattrs were only only getting
prohibited for in-inode xattrs.

						- Ted
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Patch

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index a20b57b..94df36d 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -307,7 +307,7 @@  static void check_ea_in_inode(e2fsck_t ctx, struct problem_context *pctx)
 		remain -= EXT2_EXT_ATTR_SIZE(entry->e_name_len);
 
 		/* check value size */
-		if (entry->e_value_size == 0 || entry->e_value_size > remain) {
+		if (entry->e_value_size > remain) {
 			pctx->num = entry->e_value_size;
 			problem = PR_1_ATTR_VALUE_SIZE;
 			goto fix;