2009-02-24 21:13:43

by Eric Sandeen

Subject: [PATCH] e2fsprogs: fix potential null ptr defef in check_for_modules()

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.

Signed-off-by: Eric Sandeen <[email protected]>
---

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;

2009-02-26 22:20:40

by Eric Sandeen

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 <[email protected]>
> ---
>
> 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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2009-03-06 07:38:16

by Theodore Ts'o

Subject: Re: [PATCH] e2fsprogs: fix potential null ptr defef in check_for_modules()

On Tue, Feb 24, 2009 at 03:13:39PM -0600, 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.

Thanks, applied to the e2fsprogs git tree.

- Ted