[PATCH] futex: Handle the correct robust list at compat_exit_robust_list()

[PATCH] futex: Handle the correct robust list at compat_exit_robust_list()

[André Almeida]

compat_exit_robust_list(), as exit_robust_list(), should handle the robust
list from the task_struct from the function argument, not the current task
running the function.

Fixes: 2cb5251d3d64 ("futex: Provide UABI defines for robust list entry modifiers")
Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
 kernel/futex/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index a061f54b606d..42014dcfdf0c 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -1256,7 +1256,7 @@ compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **ent
  */
 static void compat_exit_robust_list(struct task_struct *curr)
 {
-	struct compat_robust_list_head __user *head = current->futex.compat_robust_list;
+	struct compat_robust_list_head __user *head = curr->futex.compat_robust_list;
 	unsigned int limit = ROBUST_LIST_LIMIT, cur_mod, next_mod, pend_mod;
 	struct robust_list __user *entry, *next_entry, *pending;
 	compat_uptr_t uentry, next_uentry, upending;
-- 
2.55.0

Re: [PATCH] futex: Handle the correct robust list at compat_exit_robust_list()

[Thomas Gleixner]

On Mon, Sep 21 2026 at 21:54, André Almeida wrote:
> compat_exit_robust_list(), as exit_robust_list(), should handle the robust
> list from the task_struct from the function argument, not the current task
> running the function.
>
> Fixes: 2cb5251d3d64 ("futex: Provide UABI defines for robust list entry modifiers")

It actually fixes nothing because *curr is always current.

I'd rather get rid of the argument alltogether because that's just a
source of confusion.

Thanks,

        tglx

Re: [PATCH] futex: Handle the correct robust list at compat_exit_robust_list()

[André Almeida]

Em 29/09/2026 05:22, Thomas Gleixner escreveu:
> On Mon, Sep 21 2026 at 21:54, André Almeida wrote:
>> compat_exit_robust_list(), as exit_robust_list(), should handle the robust
>> list from the task_struct from the function argument, not the current task
>> running the function.
>>
>> Fixes: 2cb5251d3d64 ("futex: Provide UABI defines for robust list entry modifiers")
> 
> It actually fixes nothing because *curr is always current.
> 
> I'd rather get rid of the argument alltogether because that's just a
> source of confusion.
> 

Ack, thanks for having a look.

> Thanks,
> 
>          tglx