From: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
To: linuxppc-dev@lists.ozlabs.org,
Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
Christophe Lombard <christophe_lombard@fr.ibm.com>,
Philippe Bergheaud <philippe.bergheaud@fr.ibm.com>
Cc: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>,
Andrew Donnellan <andrew.donnellan@au1.ibm.com>,
"Alastair D'Silva" <alastair@linux.ibm.com>,
Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Subject: [PATCH 1/2] powerpc: Avoid signed to unsigned conversion in set_thread_tidr()
Date: Thu, 23 Nov 2017 18:17:17 +0530 [thread overview]
Message-ID: <20171123124718.16839-1-vaibhav@linux.vnet.ibm.com> (raw)
There is an unsafe signed to unsigned conversion in set_thread_tidr()
that may cause an error value to be assigned to SPRN_TIDR register and
used as thread-id.
The issue happens as assign_thread_tidr() returns an int and
thread.tidr is an unsigned-long. So a negative error code returned
from assign_thread_tidr() will fail the error check and gets assigned
as tidr as a large positive value.
To fix this the patch assigns the return value of assign_thread_tidr()
to a temporary int and assigns it to thread.tidr iff its '> 0'.
Fixes: ec233ede4c86("powerpc: Add support for setting SPRN_TIDR")
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
---
arch/powerpc/kernel/process.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index bfdd783e3916..a6eaf924c8b6 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1569,19 +1569,21 @@ void arch_release_task_struct(struct task_struct *t)
*/
int set_thread_tidr(struct task_struct *t)
{
+ int rc;
+
if (!cpu_has_feature(CPU_FTR_ARCH_300))
return -EINVAL;
if (t != current)
return -EINVAL;
- t->thread.tidr = assign_thread_tidr();
- if (t->thread.tidr < 0)
- return t->thread.tidr;
-
- mtspr(SPRN_TIDR, t->thread.tidr);
+ rc = assign_thread_tidr();
+ if (rc > 0) {
+ t->thread.tidr = assign_thread_tidr();
+ mtspr(SPRN_TIDR, t->thread.tidr);
+ }
- return 0;
+ return rc;
}
#endif /* CONFIG_PPC64 */
--
2.14.3
next reply other threads:[~2017-11-23 12:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-23 12:47 Vaibhav Jain [this message]
2017-11-23 12:47 ` [PATCH 2/2] powerpc: Do not assign thread.tidr if already assigned Vaibhav Jain
2017-11-24 6:17 ` [PATCH 1/2] powerpc: Avoid signed to unsigned conversion in set_thread_tidr() Michael Ellerman
2017-11-24 7:08 ` Vaibhav Jain
2017-11-27 3:44 ` Michael Ellerman
2017-11-27 17:05 ` Vaibhav Jain
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