On 1/8/25 10:04, Sebastian Andrzej Siewior wrote:
dereference_symbol_descriptor() needs to obtain the module pointer
belonging to pointer in order to resolve that pointer.
The returned mod pointer is obtained under RCU-sched/ preempt_disable()
guarantees and needs to be used within this section to ensure that the
module is not removed in the meantime.
Extend the preempt_disable() section to also cover
dereference_module_function_descriptor().
Fixes: 04b8eb7a4ccd9 ("symbol lookup: introduce dereference_symbol_descriptor()")
Cc: James E.J. Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Madhavan Srinivasan <maddy@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Naveen N Rao <naveen@xxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: linux-parisc@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Nice catch.
Acked-by: Helge Deller <deller@xxxxxx>
This patch really should be backported.
Can you add a Cc: stable tag?
Helge
---
include/linux/kallsyms.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index c3f075e8f60cb..1c6a6c1704d8d 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,10 +57,10 @@ static inline void *dereference_symbol_descriptor(void *ptr)
preempt_disable();
mod = __module_address((unsigned long)ptr);
- preempt_enable();
if (mod)
ptr = dereference_module_function_descriptor(mod, ptr);
+ preempt_enable();
#endif
return ptr;
}
