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Subject[PATCH][isapnp] Fix a potential NULL pointer dereference in isapnp_read_tag()
Date
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;

-
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