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 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) (limited to 'arch') 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" -- cgit v1.2.3