From 9254139ad083433c50ba62920107ed55fc4ca5e2 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Tue, 11 Oct 2016 14:13:38 +0200 Subject: kprobes: Avoid false KASAN reports during stack copy Kprobes save and restore raw stack chunks with memcpy(). With KASAN these chunks can contain poisoned stack redzones, as the result memcpy() interceptor produces false stack out-of-bounds reports. Use __memcpy() instead of memcpy() for stack copying. __memcpy() is not instrumented by KASAN and does not lead to the false reports. Currently there is a spew of KASAN reports during boot if CONFIG_KPROBES_SANITY_TEST is enabled: [ ] Kprobe smoke test: started [ ] ================================================================== [ ] BUG: KASAN: stack-out-of-bounds in setjmp_pre_handler+0x17c/0x280 at addr ffff88085259fba8 [ ] Read of size 64 by task swapper/0/1 [ ] page:ffffea00214967c0 count:0 mapcount:0 mapping: (null) index:0x0 [ ] flags: 0x2fffff80000000() [ ] page dumped because: kasan: bad access detected [...] Reported-by: CAI Qian Tested-by: CAI Qian Signed-off-by: Dmitry Vyukov Acked-by: Masami Hiramatsu Cc: Alexander Potapenko Cc: Alexander Shishkin Cc: Ananth N Mavinakayanahalli Cc: Andrew Morton Cc: Andrey Ryabinin Cc: Andy Lutomirski Cc: Anil S Keshavamurthy Cc: Arnaldo Carvalho de Melo Cc: Borislav Petkov Cc: Brian Gerst Cc: David S. Miller Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jiri Olsa Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: kasan-dev@googlegroups.com [ Improved various details. ] Signed-off-by: Ingo Molnar --- arch/x86/kernel/kprobes/core.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 28cee019209c..f423b0ef23a7 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1057,9 +1057,10 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) * tailcall optimization. So, to be absolutely safe * we also save and restore enough stack bytes to cover * the argument area. + * Use __memcpy() to avoid KASAN stack out-of-bounds reports as we copy + * raw stack chunk with redzones: */ - memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, - MIN_STACK_SIZE(addr)); + __memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr)); regs->flags &= ~X86_EFLAGS_IF; trace_hardirqs_off(); regs->ip = (unsigned long)(jp->entry); @@ -1118,7 +1119,7 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) /* It's OK to start function graph tracing again */ unpause_graph_tracing(); *regs = kcb->jprobe_saved_regs; - memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp)); + __memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp)); preempt_enable_no_resched(); return 1; } -- cgit v1.2.3-58-ga151 From 9f7d416c36124667c406978bcb39746589c35d7f Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Fri, 14 Oct 2016 16:07:23 +0200 Subject: kprobes: Unpoison stack in jprobe_return() for KASAN I observed false KSAN positives in the sctp code, when sctp uses jprobe_return() in jsctp_sf_eat_sack(). The stray 0xf4 in shadow memory are stack redzones: [ ] ================================================================== [ ] BUG: KASAN: stack-out-of-bounds in memcmp+0xe9/0x150 at addr ffff88005e48f480 [ ] Read of size 1 by task syz-executor/18535 [ ] page:ffffea00017923c0 count:0 mapcount:0 mapping: (null) index:0x0 [ ] flags: 0x1fffc0000000000() [ ] page dumped because: kasan: bad access detected [ ] CPU: 1 PID: 18535 Comm: syz-executor Not tainted 4.8.0+ #28 [ ] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ ] ffff88005e48f2d0 ffffffff82d2b849 ffffffff0bc91e90 fffffbfff10971e8 [ ] ffffed000bc91e90 ffffed000bc91e90 0000000000000001 0000000000000000 [ ] ffff88005e48f480 ffff88005e48f350 ffffffff817d3169 ffff88005e48f370 [ ] Call Trace: [ ] [] dump_stack+0x12e/0x185 [ ] [] kasan_report+0x489/0x4b0 [ ] [] __asan_report_load1_noabort+0x19/0x20 [ ] [] memcmp+0xe9/0x150 [ ] [] depot_save_stack+0x176/0x5c0 [ ] [] save_stack+0xb1/0xd0 [ ] [] kasan_slab_free+0x72/0xc0 [ ] [] kfree+0xc8/0x2a0 [ ] [] skb_free_head+0x79/0xb0 [ ] [] skb_release_data+0x37a/0x420 [ ] [] skb_release_all+0x4f/0x60 [ ] [] consume_skb+0x138/0x370 [ ] [] sctp_chunk_put+0xcb/0x180 [ ] [] sctp_chunk_free+0x58/0x70 [ ] [] sctp_inq_pop+0x68f/0xef0 [ ] [] sctp_assoc_bh_rcv+0xd6/0x4b0 [ ] [] sctp_inq_push+0x131/0x190 [ ] [] sctp_backlog_rcv+0xe9/0xa20 [ ... ] [ ] Memory state around the buggy address: [ ] ffff88005e48f380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ ] ffff88005e48f400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ ] >ffff88005e48f480: f4 f4 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ ] ^ [ ] ffff88005e48f500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ ] ffff88005e48f580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ ] ================================================================== KASAN stack instrumentation poisons stack redzones on function entry and unpoisons them on function exit. If a function exits abnormally (e.g. with a longjmp like jprobe_return()), stack redzones are left poisoned. Later this leads to random KASAN false reports. Unpoison stack redzones in the frames we are going to jump over before doing actual longjmp in jprobe_return(). Signed-off-by: Dmitry Vyukov Acked-by: Masami Hiramatsu Reviewed-by: Mark Rutland Cc: Mark Rutland Cc: Catalin Marinas Cc: Andrey Ryabinin Cc: Lorenzo Pieralisi Cc: Alexander Potapenko Cc: Will Deacon Cc: Andrew Morton Cc: Ananth N Mavinakayanahalli Cc: Anil S Keshavamurthy Cc: "David S. Miller" Cc: Masami Hiramatsu Cc: kasan-dev@googlegroups.com Cc: surovegin@google.com Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/1476454043-101898-1-git-send-email-dvyukov@google.com Signed-off-by: Ingo Molnar --- arch/arm64/kernel/sleep.S | 2 +- arch/x86/kernel/kprobes/core.c | 4 ++++ include/linux/kasan.h | 2 ++ mm/kasan/kasan.c | 22 +++++++++++++++++++--- 4 files changed, 26 insertions(+), 4 deletions(-) (limited to 'arch/x86') diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index b8799e7c79de..1bec41b5fda3 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -135,7 +135,7 @@ ENTRY(_cpu_resume) #ifdef CONFIG_KASAN mov x0, sp - bl kasan_unpoison_remaining_stack + bl kasan_unpoison_task_stack_below #endif ldp x19, x20, [x29, #16] diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index f423b0ef23a7..d9d8d16b69db 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -50,6 +50,7 @@ #include #include #include +#include #include #include @@ -1081,6 +1082,9 @@ void jprobe_return(void) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + /* Unpoison stack redzones in the frames we are going to jump over. */ + kasan_unpoison_stack_above_sp_to(kcb->jprobe_saved_sp); + asm volatile ( #ifdef CONFIG_X86_64 " xchg %%rbx,%%rsp \n" diff --git a/include/linux/kasan.h b/include/linux/kasan.h index d600303306eb..820c0ad54a01 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -44,6 +44,7 @@ static inline void kasan_disable_current(void) void kasan_unpoison_shadow(const void *address, size_t size); void kasan_unpoison_task_stack(struct task_struct *task); +void kasan_unpoison_stack_above_sp_to(const void *watermark); void kasan_alloc_pages(struct page *page, unsigned int order); void kasan_free_pages(struct page *page, unsigned int order); @@ -85,6 +86,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache); static inline void kasan_unpoison_shadow(const void *address, size_t size) {} static inline void kasan_unpoison_task_stack(struct task_struct *task) {} +static inline void kasan_unpoison_stack_above_sp_to(const void *watermark) {} static inline void kasan_enable_current(void) {} static inline void kasan_disable_current(void) {} diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 88af13c00d3c..70c009741aab 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -34,6 +34,7 @@ #include #include #include +#include #include "kasan.h" #include "../slab.h" @@ -62,7 +63,7 @@ void kasan_unpoison_shadow(const void *address, size_t size) } } -static void __kasan_unpoison_stack(struct task_struct *task, void *sp) +static void __kasan_unpoison_stack(struct task_struct *task, const void *sp) { void *base = task_stack_page(task); size_t size = sp - base; @@ -77,9 +78,24 @@ void kasan_unpoison_task_stack(struct task_struct *task) } /* Unpoison the stack for the current task beyond a watermark sp value. */ -asmlinkage void kasan_unpoison_remaining_stack(void *sp) +asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) { - __kasan_unpoison_stack(current, sp); + __kasan_unpoison_stack(current, watermark); +} + +/* + * Clear all poison for the region between the current SP and a provided + * watermark value, as is sometimes required prior to hand-crafted asm function + * returns in the middle of functions. + */ +void kasan_unpoison_stack_above_sp_to(const void *watermark) +{ + const void *sp = __builtin_frame_address(0); + size_t size = watermark - sp; + + if (WARN_ON(sp > watermark)) + return; + kasan_unpoison_shadow(sp, size); } /* -- cgit v1.2.3-58-ga151 From 5c38181ce9c5182377e79271a3ed0a2d0e999c33 Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Fri, 14 Oct 2016 10:29:08 +0300 Subject: perf/x86/intel: Remove an inconsistent NULL check Smatch complains that we don't check "event->ctx" consistently. It's never NULL so we can just remove the check. Signed-off-by: Dan Carpenter Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: David Carrillo-Cisneros Cc: Jiri Olsa Cc: Kan Liang Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: kernel-janitors@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/events/intel/lbr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c index fc6cf21c535e..81b321ace8e0 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -458,8 +458,8 @@ void intel_pmu_lbr_del(struct perf_event *event) if (!x86_pmu.lbr_nr) return; - if (branch_user_callstack(cpuc->br_sel) && event->ctx && - event->ctx->task_ctx_data) { + if (branch_user_callstack(cpuc->br_sel) && + event->ctx->task_ctx_data) { task_ctx = event->ctx->task_ctx_data; task_ctx->lbr_callstack_users--; } -- cgit v1.2.3-58-ga151