nptl: Don't madvise user provided stack

User provided stack should not be released nor madvised at
thread exit because it's owned by the user.

If the memory is shared or file based then MADV_DONTNEED
can have unwanted effects. With memory tagging on aarch64
linux the tags are dropped and thus it may invalidate
pointers.

Tested on aarch64-linux-gnu with MTE, it fixes

FAIL: nptl/tst-stack3
FAIL: nptl/tst-stack3-mem

diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 35a9927cf25c1f6a3f90d295fd30dc482abd4a75..6d6ab88960e64bac37daf8711bc987fc69befd38 100644 (file)
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -549,8 +549,9 @@ START_THREAD_DEFN
     }
 #endif
 
-  advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
-                     pd->guardsize);
+  if (!pd->user_stack)
+    advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
+                       pd->guardsize);
 
   if (__glibc_unlikely (pd->cancelhandling & SETXID_BITMASK))
     {