linux-ext4 - Re: [PATCH] e2fsprogs: fix potential null ptr deref in check_for

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Date:	Thu, 26 Feb 2009 16:20:37 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] e2fsprogs: fix potential null ptr deref in check_for_modules()

Eric Sandeen wrote:
> The coverity scanner found this one.
> 
> If a line in modules.dep has a ":" but no "/" then:
> 
>                 if ((cp = strchr(buf, ':')) != NULL)
>                         *cp = 0;
>                 else
>                         continue;
>                 if ((cp = strrchr(buf, '/')) != NULL)
>                         cp++;
>                 /* XXX else cp is still null */
>                 i = strlen(cp);
> 
> ... we will deref a null pointer (cp).  This can be 
> demonstrated by putting a line like:
> 
> foo.ko:
> 
> into modules.dep.  The below change just says that if no "/" is
> found, treat the whole string as the module name.

FWIW; this resolves RH bugzilla:
[Bug 486997] rawhide's init/nash segfaults in libblkid

and also is an extension of the patch Jim sent a couple days ago.

The issue is that for fedora initrds, anyway, modules dep is something like:

crc16.ko:
ext4.ko: jbd2.ko crc16.ko
...

so it hits exactly this case.

-Eric

> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> ---
> 
> Index: e2fsprogs/e2fsck/util.c
> ===================================================================
> --- e2fsprogs.orig/e2fsck/util.c
> +++ e2fsprogs/e2fsck/util.c
> @@ -663,6 +663,8 @@ int check_for_modules(const char *fs_nam
>  			continue;
>  		if ((cp = strrchr(buf, '/')) != NULL)
>  			cp++;
> +		else
> +			cp = buf;
>  		i = strlen(cp);
>  		if (i > 3) {
>  			t = cp + i - 3;
> Index: e2fsprogs/lib/blkid/probe.c
> ===================================================================
> --- e2fsprogs.orig/lib/blkid/probe.c
> +++ e2fsprogs/lib/blkid/probe.c
> @@ -227,6 +227,8 @@ static int check_for_modules(const char 
>  			continue;
>  		if ((cp = strrchr(buf, '/')) != NULL)
>  			cp++;
> +		else
> +			cp = buf;
>  		i = strlen(cp);
>  		if (i > 3) {
>  			t = cp + i - 3;
> 
> --
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