lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sun, 1 Jun 2008 20:08:42 -0400
From:	Theodore Tso <>
To:	"Aneesh Kumar K.V" <>
Subject: Re: [PATCH] ext4: Fix use of uninitialized data

On Thu, May 15, 2008 at 12:17:11AM +0530, Aneesh Kumar K.V wrote:
> @@ -3134,8 +3135,7 @@ static void ext4_mb_use_inode_pa(struct ext4_allocation_context *ac,
>  static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
>  				struct ext4_prealloc_space *pa)
>  {
> -	unsigned len = ac->ac_o_ex.fe_len;
> -
> +	unsigned int len = ac->ac_o_ex.fe_len;
>  	ext4_get_group_no_and_offset(ac->ac_sb, pa->pa_pstart,
>  					&ac->ac_b_ex.fe_group,
>  					&ac->ac_b_ex.fe_start);
> -- 

This change had nothing to do with fixing the use of unitialized data,
but when I started looking more closely, it raised a potential signed
vs. unsigned issue: ac_o_ex is a struct ext4_free_extent, and fe_len
is an int.

So here we are assigning an int to an unsigned int.  Later, len is
assigned to ac_b_ex.len, which means assigning an unsigned int to an
int.  In other places, fe_len (an int) is compared against pa_free
(which is an unsigned short), and fe_len gets assined to pa_free, once
again mixing signed and unsigned.

Can someone who is really familiar with this code check this out?  I
think the following pseudo-patch to mballoc.h might be in order:

 struct ext4_free_extent {
 	ext4_lblk_t fe_logical;
 	ext4_grpblk_t fe_start;
 	ext4_group_t fe_group;
-	int fe_len;
+	unsigned int fe_len;

						- Ted
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists