From: Benjamin Herrenschmidt Date: Sun, 27 May 2007 05:18:22 +0000 (+1000) Subject: [POWERPC] Fix possible access to free pages X-Git-Tag: v2.6.22-rc4~12^2~10 X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=6ad8d010b2f364b739020e514e61b6a73444464b;p=linux-2.6-omap-h63xx.git [POWERPC] Fix possible access to free pages I think we have a subtle race on ppc64 with the tlb batching. The common code expects tlb_flush() to actually flush any pending TLB batch. It does that because it delays all page freeing until after tlb_flush() is called, in order to ensure no stale reference to those pages exist in any TLB, thus causing potential access to the freed pages. However, our tlb_flush only triggers the RCU for freeing page table pages, it does not currently trigger a flush of a pending TLB/hash batch, which is, I think, an error. This fixes it. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras --- diff --git a/include/asm-powerpc/tlb.h b/include/asm-powerpc/tlb.h index 0a17682663d..66714042e43 100644 --- a/include/asm-powerpc/tlb.h +++ b/include/asm-powerpc/tlb.h @@ -38,6 +38,15 @@ extern void pte_free_finish(void); static inline void tlb_flush(struct mmu_gather *tlb) { + struct ppc64_tlb_batch *tlbbatch = &__get_cpu_var(ppc64_tlb_batch); + + /* If there's a TLB batch pending, then we must flush it because the + * pages are going to be freed and we really don't want to have a CPU + * access a freed page because it has a stale TLB + */ + if (tlbbatch->index) + __flush_tlb_pending(tlbbatch); + pte_free_finish(); }