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SubjectRe: [PATCH][isapnp] Fix a potential NULL pointer dereference in isapnp_read_tag()
On Sun, 1 Jul 2007 01:38:31 +0200
Jesper Juhl <jesper.juhl@gmail.com> wrote:

> The Coverity checker spotted (as bug #809) that we dereference 'type'
> long before we actually test it against NULL in
> drivers/pnp/isapnp/core.c::isapnp_read_tag() - both branches of the
> 'if (tag & 0x80)' dereference type, and since this 'if' is before the test
> against NULL and the return of -1, this will blow up is ever type is NULL.
> This is easy to fix by simply moving the NULL test to the beginning of
> the function.
>
>
> Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
> ---
>
> drivers/pnp/isapnp/core.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
> diff --git a/drivers/pnp/isapnp/core.c b/drivers/pnp/isapnp/core.c
> index a0b1587..5696924 100644
> --- a/drivers/pnp/isapnp/core.c
> +++ b/drivers/pnp/isapnp/core.c
> @@ -356,6 +356,8 @@ static int __init isapnp_read_tag(unsigned char *type, unsigned short *size)
> {
> unsigned char tag, tmp[2];
>
> + if (!type) /* wrong type */
> + return -1;
> isapnp_peek(&tag, 1);
> if (tag == 0) /* invalid tag */
> return -1;
> @@ -370,8 +372,6 @@ static int __init isapnp_read_tag(unsigned char *type, unsigned short *size)
> #if 0
> printk(KERN_DEBUG "tag = 0x%x, type = 0x%x, size = %i\n", tag, *type, *size);
> #endif
> - if (type == 0) /* wrong type */
> - return -1;
> if (*type == 0xff && *size == 0xffff) /* probably invalid data */
> return -1;
> return 0;

dood, look at the callers. NULL is not possible here.
-
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