unwind: Fix unwind_deferred_request() vs NMI

task_work_add(RWA_RESUME) isn't NMI-safe, use TWA_NMI_CURRENT when
used from NMI context.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://patch.msgid.link/20250924080119.005422353@infradead.org

diff --git a/kernel/unwind/deferred.c b/kernel/unwind/deferred.c
index dc6040aae3ee1949e91e01386556549f1ab95f80..d2cd3a7fd286dfe6bac088ee0a0b8123ecfe5a6b 100644 (file)
--- a/kernel/unwind/deferred.c
+++ b/kernel/unwind/deferred.c
@@ -231,6 +231,7 @@ void unwind_deferred_task_exit(struct task_struct *task)
 int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
 {
        struct unwind_task_info *info = &current->unwind_info;
+       int twa_mode = TWA_RESUME;
        unsigned long old, bits;
        unsigned long bit;
        int ret;
@@ -246,8 +247,11 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
         * Trigger a warning to make it obvious that an architecture
         * is using this in NMI when it should not be.
         */
-       if (WARN_ON_ONCE(!CAN_USE_IN_NMI && in_nmi()))
-               return -EINVAL;
+       if (in_nmi()) {
+               if (WARN_ON_ONCE(!CAN_USE_IN_NMI))
+                       return -EINVAL;
+               twa_mode = TWA_NMI_CURRENT;
+       }
 
        /* Do not allow cancelled works to request again */
        bit = READ_ONCE(work->bit);
@@ -285,7 +289,7 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
        }
 
        /* The work has been claimed, now schedule it. */
-       ret = task_work_add(current, &info->work, TWA_RESUME);
+       ret = task_work_add(current, &info->work, twa_mode);
 
        if (WARN_ON_ONCE(ret))
                WRITE_ONCE(info->unwind_mask, 0);