+ mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch added to -mm tree

* + mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch added to -mm tree
@ 2022-01-27  2:55 akpm
  2022-01-27 15:45 ` Manfred Spraul
  0 siblings, 1 reply; 3+ messages in thread
From: akpm @ 2022-01-27  2:55 UTC (permalink / raw)
  To: 1vier1, arnd, cgel.zte, chi.minghao, dbueso, manfred, mhocko,
	mm-commits, rdunlap, shakeelb, stable, unixbhaskar, urezki, vvs,
	zealci


The patch titled
     Subject: mm/util.c: make kvfree() safe for calling while holding spinlocks
has been added to the -mm tree.  Its filename is
     mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch

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------------------------------------------------------
From: Manfred Spraul <manfred@colorfullife.com>
Subject: mm/util.c: make kvfree() safe for calling while holding spinlocks

One codepath in find_alloc_undo() calls kvfree() while holding a spinlock.
Since vfree() can sleep this is a bug.

Previously, the code path used kfree(), and kfree() is safe to be called
while holding a spinlock.

Minghao proposed to fix this by updating find_alloc_undo().

Alternate proposal to fix this: Instead of changing find_alloc_undo(),
change kvfree() so that the same rules as for kfree() apply: Having
different rules for kfree() and kvfree() just asks for bugs.

Disadvantage: Releasing vmalloc'ed memory will be delayed a bit.

Link: https://lkml.kernel.org/r/20211222194828.15320-1-manfred@colorfullife.com
Link: https://lore.kernel.org/all/20211222081026.484058-1-chi.minghao@zte.com.cn/
Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo allocation")
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Reported-by: Minghao Chi <chi.minghao@zte.com.cn>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: CGEL ZTE <cgel.zte@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <1vier1@web.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/util.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/util.c~mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks
+++ a/mm/util.c
@@ -603,12 +603,12 @@ EXPORT_SYMBOL(kvmalloc_node);
  * It is slightly more efficient to use kfree() or vfree() if you are certain
  * that you know which one to use.
  *
- * Context: Either preemptible task context or not-NMI interrupt.
+ * Context: Any context except NMI interrupt.
  */
 void kvfree(const void *addr)
 {
 	if (is_vmalloc_addr(addr))
-		vfree(addr);
+		vfree_atomic(addr);
 	else
 		kfree(addr);
 }
_

Patches currently in -mm which might be from manfred@colorfullife.com are

mm-utilc-make-kvfree-safe-for-calling-while-holding-spinlocks.patch


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