linux-kernel - Re: [PATCH] fix sys_prctl() returned uninitialized value

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Message-Id: <20080521222551.8d8e064a.akpm@linux-foundation.org>
Date:	Wed, 21 May 2008 22:25:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Andrew G. Morgan" <morgan@...nel.org>
Cc:	Shi Weihua <shiwh@...fujitsu.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	linux-security-module@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, jmorris@...ei.org,
	ltp-list@...ts.sourceforge.net
Subject: Re: [PATCH] fix sys_prctl() returned uninitialized value

On Wed, 21 May 2008 22:01:17 -0700 "Andrew G. Morgan" <morgan@...nel.org> wrote:

> this is the default expected by the subsequent switch ().
> 
> Signed-off-by: Andrew G. Morgan <morgan@...nel.org>
> ---
>  kernel/sys.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 895d2d4..cb25a64 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1657,6 +1657,8 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
>  	if (security_task_prctl(option, arg2, arg3, arg4, arg5, &error))
>  		return error;
>  
> +	error = 0;
> +
>  	switch (option) {
>  		case PR_SET_PDEATHSIG:
>  			if (!valid_signal(arg2)) {

Looking at it some more there are two cases which don't initialise
`error': PR_SET_PDEATHSIG and PR_SET_DUMPABLE.  (let's set aside the
silliness of having sys_prctl() perform set_dumpable()'s argument
checking for it).

So I would propose this fix, mainly because it removes that nasty
uninitialized_var().  Please review carefully.



From: Shi Weihua <shiwh@...fujitsu.com> 

If none of the switch cases match, the PR_SET_PDEATHSIG and
PR_SET_DUMPABLE cases of the switch statement will never write to local
variable `error'.

Signed-off-by: Shi Weihua <shiwh@...fujitsu.com> 
Cc: Andrew G. Morgan <morgan@...nel.org>
Cc: "Serge E. Hallyn" <serue@...ibm.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 kernel/sys.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff -puN kernel/sys.c~sys_prctl-fix-return-of-uninitialized-value kernel/sys.c
--- a/kernel/sys.c~sys_prctl-fix-return-of-uninitialized-value
+++ a/kernel/sys.c
@@ -1652,7 +1652,7 @@ asmlinkage long sys_umask(int mask)
 asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 			  unsigned long arg4, unsigned long arg5)
 {
-	long uninitialized_var(error);
+	long error = 0;
 
 	if (security_task_prctl(option, arg2, arg3, arg4, arg5, &error))
 		return error;
@@ -1701,9 +1701,7 @@ asmlinkage long sys_prctl(int option, un
 			error = PR_TIMING_STATISTICAL;
 			break;
 		case PR_SET_TIMING:
-			if (arg2 == PR_TIMING_STATISTICAL)
-				error = 0;
-			else
+			if (arg2 != PR_TIMING_STATISTICAL)
 				error = -EINVAL;
 			break;
 
_

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