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'.
The patch shouldn't impact the calling convention of set_thread_tidr()
i.e all -ve return-values are error codes and a return value of '0'
indicates success.
Fixes: ec233ede4c86("powerpc: Add support for setting SPRN_TIDR")
Signed-off-by: Vaibhav Jain <vaib...@linux.vnet.ibm.com>
---
Changelog:
v4 -> Simplified the code flow [Sukadev]
v3 -> Updated the patch to not impact the calling convention [Mpe, Christophe]
v2 -> * Update the patch description to document the calling
convention of set_thread_tidr(). [Mpe]
* Fix a tidr allocation leak.
---
arch/powerpc/kernel/process.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index bfdd783e3916..d205b52e3850 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1569,16 +1569,19 @@ 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;
+ rc = assign_thread_tidr();
+ if (rc < 0)
+ return rc;
+ t->thread.tidr = rc;
mtspr(SPRN_TIDR, t->thread.tidr);
return 0;
--
2.14.3
