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-call... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-utilc-make-kvfree-safe-for-call...

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated there every 3-4 working days

------------------------------------------------------ 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