From: Dmitry Vyukov <[email protected]> This warning does not seem to be useful. Most of the time it fires when allocation size depends on syscall arguments. We could add __GFP_NOWARN to these allocation sites, but having a warning only to suppress it does not make lots of sense. Moreover, this warnings never fires for constant-size allocations and never for slub, because there are additional checks and fallback to kmalloc_large() for large allocations and kmalloc_large() does not warn. So the warning only fires for non-constant allocations and only with slab, which is odd to begin with. The warning leads to episodic unuseful syzbot reports. Remote it.
While we are here also fix the check. We should check against KMALLOC_MAX_CACHE_SIZE rather than KMALLOC_MAX_SIZE. It all kinda worked because for slab the constants are the same, and slub always checks the size against KMALLOC_MAX_CACHE_SIZE before kmalloc_slab(). But if we get there with size > KMALLOC_MAX_CACHE_SIZE anyhow bad things will happen. Signed-off-by: Dmitry Vyukov <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: David Rientjes <[email protected]> Cc: Joonsoo Kim <[email protected]> Cc: Andrew Morton <[email protected]> Cc: [email protected] Cc: [email protected] Reported-by: [email protected] Reported-by: [email protected] Reported-by: [email protected] Reported-by: [email protected] Reported-by: [email protected] --- mm/slab_common.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 1f903589980f9..2733bddcfdc0c 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1023,10 +1023,8 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) { unsigned int index; - if (unlikely(size > KMALLOC_MAX_SIZE)) { - WARN_ON_ONCE(!(flags & __GFP_NOWARN)); + if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) return NULL; - } if (size <= 192) { if (!size) -- 2.19.0.605.g01d371f741-goog
