From 467ab8be5592855fb4a389bd43236b29e3ae1ad2 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Thu, 15 Jan 2009 13:51:21 -0800 Subject: [PATCH] lib/idr.c: use kmem_cache_zalloc() for the idr_layer cache commit 5b019e99016f3a692ba45bf68fba73a402d7c01a upstream. David points out that the idr_remove_all() function returns unused slabs to the kmem cache, but needs to zero them first or else they will be uninitialized upon next use. This causes crashes which have been observed in the firewire subsystem. He fixed this by zeroing the object before freeing it in idr_remove_all(). But we agree that simply removing the constructor and zeroing the object at allocation time is simpler than relying upon slab constructor machinery and might even be faster. This problem was introduced by "idr: make idr_remove rcu-safe" (commit cf481c20c476ad2c0febdace9ce23f5a4db19582), which was first released in 2.6.27. There are no known codesites which trigger this bug in 2.6.27 or 2.6.28. The post-2.6.28 firewire changes are the only known triggerer. There might of course be not-yet-discovered triggerers in 2.6.27 and 2.6.28, and there might be out-of-tree triggerers which are added to those kernel versions. I'll let the -stable guys decide whether they want to backport this fix. Reported-by: David Moore Cc: Stefan Richter Cc: Nadia Derbey Cc: Paul E. McKenney Cc: Manfred Spraul Cc: Kristian Hgsberg Acked-by: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- lib/idr.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index 1c4f9281f412..21154aea67e8 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -121,7 +121,7 @@ int idr_pre_get(struct idr *idp, gfp_t gfp_mask) { while (idp->id_free_cnt < IDR_FREE_MAX) { struct idr_layer *new; - new = kmem_cache_alloc(idr_layer_cache, gfp_mask); + new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); if (new == NULL) return (0); move_to_free_list(idp, new); @@ -623,16 +623,10 @@ void *idr_replace(struct idr *idp, void *ptr, int id) } EXPORT_SYMBOL(idr_replace); -static void idr_cache_ctor(void *idr_layer) -{ - memset(idr_layer, 0, sizeof(struct idr_layer)); -} - void __init idr_init_cache(void) { idr_layer_cache = kmem_cache_create("idr_layer_cache", - sizeof(struct idr_layer), 0, SLAB_PANIC, - idr_cache_ctor); + sizeof(struct idr_layer), 0, SLAB_PANIC, NULL); } /** -- 2.39.5