From d34fda4a84c18402640a1a2342d6e6d9829e6db7 Mon Sep 17 00:00:00 2001 From: Chris Wright Date: Sat, 18 Aug 2007 14:31:41 -0700 Subject: [PATCH] x86: properly initialize temp insn buffer for paravirt patching With commit ab144f5ec64c42218a555ec1dbde6b60cf2982d6 the patching code now collects the complete new instruction stream into a temp buffer before finally patching in the new insns. In some cases the paravirt patchers will choose to leave the patch site unpatched (length mismatch, clobbers mismatch, etc). This causes the new patching code to copy an uninitialized temp buffer, i.e. garbage, to the callsite. Simply make sure to always initialize the buffer with the original instruction stream. A better fix is to audit all the patchers and return proper length so that apply_paravirt() can skip copies when we leave the patch site untouched. Signed-off-by: Chris Wright Signed-off-by: Linus Torvalds --- arch/i386/kernel/alternative.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c index 1b66d5c70e..9f4ac8b02d 100644 --- a/arch/i386/kernel/alternative.c +++ b/arch/i386/kernel/alternative.c @@ -366,6 +366,8 @@ void apply_paravirt(struct paravirt_patch_site *start, unsigned int used; BUG_ON(p->len > MAX_PATCH_LEN); + /* prep the buffer with the original instructions */ + memcpy(insnbuf, p->instr, p->len); used = paravirt_ops.patch(p->instrtype, p->clobbers, insnbuf, (unsigned long)p->instr, p->len); -- 2.39.5