On Thu, Nov 10, 2022 at 04:44:59PM +0100, Vlastimil Babka wrote: > On 11/10/22 13:57, Feng Tang wrote: > > On Thu, Nov 10, 2022 at 11:20:34AM +0800, Tang, Feng wrote: > >> On Wed, Nov 09, 2022 at 03:28:19PM +0100, Vlastimil Babka wrote: > > [...] > >> > > + /* > >> > > + * For kmalloc object, the allocated memory size(object_size) is likely > >> > > + * larger than the requested size(orig_size). If redzone check is > >> > > + * enabled for the extra space, don't zero it, as it will be redzoned > >> > > + * soon. The redzone operation for this extra space could be seen as a > >> > > + * replacement of current poisoning under certain debug option, and > >> > > + * won't break other sanity checks. > >> > > + */ > >> > > + if (kmem_cache_debug_flags(s, SLAB_STORE_USER) && > >> > > >> > Shouldn't we check SLAB_RED_ZONE instead? Otherwise a debugging could be > >> > specified so that SLAB_RED_ZONE is set but SLAB_STORE_USER? > >> > >> Thanks for the catch! > >> > >> I will add check for SLAB_RED_ZONE. The SLAB_STORE_USER is for > >> checking whether 'orig_size' field exists. In earlier discussion, > >> we make 'orig_size' depend on STORE_USER, https://lore.kernel.org/lkml/1b0fa66c-f855-1c00-e024-b2b823b18678@xxxxxxx/ > > > > Below is the updated patch, please review, thanks! > > Thanks, grabbing it including Andrey's review, with a small change below: > > > - Feng > > > > -----8>---- > > From b2a92f0c2518ef80fcda340f1ad37b418ee32d85 Mon Sep 17 00:00:00 2001 > > From: Feng Tang <feng.tang@xxxxxxxxx> > > Date: Thu, 20 Oct 2022 20:47:31 +0800 > > Subject: [PATCH 1/3] mm/slub: only zero requested size of buffer for kzalloc > > when debug enabled [...] > > + /* > > + * For kmalloc object, the allocated memory size(object_size) is likely > > + * larger than the requested size(orig_size). If redzone check is > > + * enabled for the extra space, don't zero it, as it will be redzoned > > + * soon. The redzone operation for this extra space could be seen as a > > + * replacement of current poisoning under certain debug option, and > > + * won't break other sanity checks. > > + */ > > + if (kmem_cache_debug_flags(s, SLAB_STORE_USER) && > > + (s->flags & SLAB_RED_ZONE) && > > Combined the two above to: > > if (kmem_cache_debug_flags(s, SLAB_STORE_USER | SLAB_RED_ZONE) Yes, this is cleaner, thanks! - Feng
