From 092d0f6044bd38376a6ed8b042f1d2fbc53875d7 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Thu, 30 Apr 2009 15:05:42 +0200 Subject: SLQB: fix dumb early allocation cache The dumb early allocation cache had a bug where it could allow allocation to go past the end of a page, which could cause crashes or random memory corruption. Fix this and simplify the logic. Tested-by: Stephen Rothwell Signed-off-by: Nick Piggin --- mm/slqb.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/mm/slqb.c b/mm/slqb.c index a6518433bdda..2252070fac66 100644 --- a/mm/slqb.c +++ b/mm/slqb.c @@ -2185,8 +2185,11 @@ static void *kmem_cache_dyn_array_alloc(int ids) { size_t size = sizeof(void *) * ids; + BUG_ON(!size); + if (unlikely(!slab_is_available())) { static void *nextmem; + static size_t nextleft; void *ret; /* @@ -2194,16 +2197,16 @@ static void *kmem_cache_dyn_array_alloc(int ids) * never get freed by definition so we can do it rather * simply. */ - if (!nextmem) { - nextmem = alloc_pages_exact(size, GFP_KERNEL); - if (!nextmem) - return NULL; + if (size > nextleft) { + nextmem = alloc_pages_exact(size, GFP_KERNEL); + if (!nextmem) + return NULL; + nextleft = roundup(size, PAGE_SIZE); } + ret = nextmem; - nextmem = (void *)((unsigned long)ret + size); - if ((unsigned long)ret >> PAGE_SHIFT != - (unsigned long)nextmem >> PAGE_SHIFT) - nextmem = NULL; + nextleft -= size; + nextmem += size; memset(ret, 0, size); return ret; } else { -- cgit v1.2.3