From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
alexei.starovoitov@gmail.com, alyssa.milburn@intel.com,
andrew.cooper3@citrix.com, hjl.tools@gmail.com,
joao@overdrivepizza.com, jpoimboe@redhat.com,
keescook@chromium.org, linux-kernel@vger.kernel.org,
mark.rutland@arm.com, mbenes@suse.cz, ndesaulniers@google.com,
samitolvanen@google.com, x86@kernel.org
Subject: Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location
Date: Wed, 2 Mar 2022 21:51:36 +0100 [thread overview]
Message-ID: <Yh/Y2FHw90m00owK@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220302144716.1772020c@gandalf.local.home>
On Wed, Mar 02, 2022 at 02:47:16PM -0500, Steven Rostedt wrote:
> Note, I just pulled this patch, and I hit this warning:
>
> WARNING: CPU: 0 PID: 6965 at arch/x86/kernel/kprobes/core.c:205 recover_probed_instruction+0x8f/0xa0
>
> static unsigned long
> __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
> {
> struct kprobe *kp;
> unsigned long faddr;
>
> kp = get_kprobe((void *)addr);
> faddr = ftrace_location(addr);
> /*
> * Addresses inside the ftrace location are refused by
> * arch_check_ftrace_location(). Something went terribly wrong
> * if such an address is checked here.
> */
> if (WARN_ON(faddr && faddr != addr)) <<---- HERE
> return 0UL;
Ha! so a bunch of IRC later I figured out how it is possible you hit
this with just the patch on and how I legitimately hit this and what to
do about it.
Your problem seems to be that we got ftrace_location() wrong in that
lookup_rec()'s end argument is inclusive, hence we need:
lookup_rec(ip, ip + size - 1)
Now, the above thing asserts that:
ftrace_location(x) == {0, x}
and that is genuinely false in my case, I get x+4 as additional possible
output. So I think I need the below change to go on top of all I have:
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 7f0ce42f8ff9..4c13406e0bc4 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -198,13 +198,14 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
kp = get_kprobe((void *)addr);
faddr = ftrace_location(addr);
+
/*
- * Addresses inside the ftrace location are refused by
- * arch_check_ftrace_location(). Something went terribly wrong
- * if such an address is checked here.
+ * In case addr maps to sym+0 ftrace_location() might return something
+ * other than faddr. In that case consider it the same as !faddr.
*/
- if (WARN_ON(faddr && faddr != addr))
- return 0UL;
+ if (faddr && faddr != addr)
+ faddr = 0;
+
/*
* Use the current code if it is not modified by Kprobe
* and it cannot be modified by ftrace.
next prev parent reply other threads:[~2022-03-02 20:52 UTC|newest]
Thread overview: 183+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-24 14:51 [PATCH v2 00/39] x86: Kernel IBT Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 01/39] kbuild: Fix clang build Peter Zijlstra
2022-02-25 0:11 ` Kees Cook
2022-03-01 21:16 ` Nick Desaulniers
2022-03-02 0:47 ` Kees Cook
2022-03-02 0:53 ` Fangrui Song
2022-03-02 16:37 ` Nathan Chancellor
2022-03-02 18:40 ` Kees Cook
2022-03-02 19:18 ` Nick Desaulniers
2022-03-02 21:15 ` Nathan Chancellor
2022-03-02 22:07 ` Nick Desaulniers
2022-03-02 23:00 ` Kees Cook
2022-03-02 23:10 ` Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 02/39] static_call: Avoid building empty .static_call_sites Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 03/39] x86/module: Fix the paravirt vs alternative order Peter Zijlstra
2022-03-01 14:37 ` Miroslav Benes
2022-02-24 14:51 ` [PATCH v2 04/39] objtool: Add --dry-run Peter Zijlstra
2022-02-25 0:27 ` Kees Cook
2022-03-01 14:37 ` Miroslav Benes
2022-02-24 14:51 ` [PATCH v2 05/39] x86: Base IBT bits Peter Zijlstra
2022-02-25 0:35 ` Kees Cook
2022-02-25 0:46 ` Nathan Chancellor
2022-02-25 22:08 ` Nathan Chancellor
2022-02-26 0:29 ` Joao Moreira
2022-02-26 4:58 ` Kees Cook
2022-02-26 4:59 ` Fāng-ruì Sòng
2022-02-26 5:04 ` Kees Cook
2022-02-25 13:41 ` Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 06/39] x86/ibt: Add ANNOTATE_NOENDBR Peter Zijlstra
2022-02-25 0:36 ` Kees Cook
2022-02-24 14:51 ` [PATCH v2 07/39] x86/entry: Sprinkle ENDBR dust Peter Zijlstra
2022-02-24 22:37 ` Josh Poimboeuf
2022-02-25 0:42 ` Kees Cook
2022-02-25 9:22 ` Andrew Cooper
2022-02-24 14:51 ` [PATCH v2 08/39] x86/linkage: Add ENDBR to SYM_FUNC_START*() Peter Zijlstra
2022-02-25 0:45 ` Kees Cook
2022-02-24 14:51 ` [PATCH v2 09/39] x86/ibt,paravirt: Sprinkle ENDBR Peter Zijlstra
2022-02-25 0:47 ` Kees Cook
2022-02-24 14:51 ` [PATCH v2 10/39] x86/ibt,crypto: Add ENDBR for the jump-table entries Peter Zijlstra
2022-02-24 22:41 ` Josh Poimboeuf
2022-02-25 0:50 ` Kees Cook
2022-02-25 10:22 ` Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 11/39] x86/ibt,kvm: Add ENDBR to fastops Peter Zijlstra
2022-02-25 0:54 ` Kees Cook
2022-02-25 10:24 ` Peter Zijlstra
2022-02-25 13:09 ` David Laight
2022-02-24 14:51 ` [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location Peter Zijlstra
2022-02-24 15:55 ` Masami Hiramatsu
2022-02-24 15:58 ` Steven Rostedt
2022-02-24 15:59 ` Steven Rostedt
2022-02-24 16:01 ` Steven Rostedt
2022-02-24 22:46 ` Josh Poimboeuf
2022-02-24 22:51 ` Steven Rostedt
2022-02-25 1:34 ` Masami Hiramatsu
2022-02-25 2:19 ` Steven Rostedt
2022-02-25 10:20 ` Masami Hiramatsu
2022-02-25 13:36 ` Steven Rostedt
2022-03-01 18:57 ` Naveen N. Rao
2022-03-01 19:20 ` Steven Rostedt
2022-03-02 13:20 ` Peter Zijlstra
2022-03-02 16:01 ` Steven Rostedt
2022-03-02 19:47 ` Steven Rostedt
2022-03-02 20:48 ` Steven Rostedt
2022-03-02 20:51 ` Peter Zijlstra [this message]
2022-03-03 9:45 ` Naveen N. Rao
2022-03-03 13:04 ` Peter Zijlstra
2022-03-03 14:34 ` Steven Rostedt
2022-03-03 15:59 ` Peter Zijlstra
2022-03-06 3:48 ` Masami Hiramatsu
2022-03-09 11:47 ` Naveen N. Rao
2022-03-03 14:39 ` Naveen N. Rao
2022-02-25 0:55 ` Kees Cook
2022-03-02 16:25 ` Naveen N. Rao
2022-02-24 14:51 ` [PATCH v2 13/39] x86/livepatch: Validate " Peter Zijlstra
2022-02-24 23:02 ` Josh Poimboeuf
2022-02-24 14:51 ` [PATCH v2 14/39] x86/ibt,ftrace: Make function-graph play nice Peter Zijlstra
2022-02-24 15:36 ` Peter Zijlstra
2022-02-24 15:42 ` Steven Rostedt
2022-02-24 23:09 ` Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 15/39] x86/ibt,kprobes: Fix more +0 assumptions Peter Zijlstra
2022-02-25 0:58 ` Kees Cook
2022-02-25 1:32 ` Masami Hiramatsu
2022-02-25 10:46 ` Peter Zijlstra
2022-02-25 13:42 ` Masami Hiramatsu
2022-02-25 15:41 ` Peter Zijlstra
2022-02-26 2:10 ` Masami Hiramatsu
2022-02-26 11:48 ` Peter Zijlstra
2022-02-25 14:14 ` Steven Rostedt
2022-02-26 7:09 ` Masami Hiramatsu
2022-02-28 6:07 ` Masami Hiramatsu
2022-02-28 23:25 ` Peter Zijlstra
2022-03-01 2:49 ` Masami Hiramatsu
2022-03-01 8:28 ` Peter Zijlstra
2022-03-01 17:19 ` Naveen N. Rao
2022-03-01 19:12 ` Peter Zijlstra
2022-03-01 20:05 ` Peter Zijlstra
2022-03-02 15:59 ` Naveen N. Rao
2022-03-02 16:38 ` Peter Zijlstra
2022-03-02 16:17 ` Naveen N. Rao
2022-03-02 19:32 ` Peter Zijlstra
2022-03-02 19:39 ` Peter Zijlstra
2022-03-03 12:11 ` Naveen N. Rao
2022-03-03 1:54 ` Masami Hiramatsu
2022-03-02 0:11 ` Masami Hiramatsu
2022-03-02 10:25 ` Peter Zijlstra
2022-03-01 17:03 ` Naveen N. Rao
2022-02-24 14:51 ` [PATCH v2 16/39] x86/bpf: Add ENDBR instructions to prologue and trampoline Peter Zijlstra
2022-02-24 23:37 ` Josh Poimboeuf
2022-02-25 0:59 ` Kees Cook
2022-02-25 11:20 ` Peter Zijlstra
2022-02-25 12:24 ` Peter Zijlstra
2022-02-25 22:46 ` Josh Poimboeuf
2022-02-24 14:51 ` [PATCH v2 17/39] x86/ibt,ftrace: Add ENDBR to samples/ftrace Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 18/39] x86/ibt: Add IBT feature, MSR and #CP handling Peter Zijlstra
2022-02-24 23:55 ` Josh Poimboeuf
2022-02-25 10:51 ` Peter Zijlstra
2022-02-25 11:10 ` Peter Zijlstra
2022-02-25 23:51 ` Josh Poimboeuf
2022-02-26 11:55 ` Peter Zijlstra
2022-02-25 1:09 ` Kees Cook
2022-02-25 19:59 ` Edgecombe, Rick P
2022-03-01 15:14 ` Peter Zijlstra
2022-03-01 21:02 ` Peter Zijlstra
2022-03-01 23:13 ` Josh Poimboeuf
2022-03-02 1:59 ` Edgecombe, Rick P
2022-03-02 13:49 ` Peter Zijlstra
2022-03-02 18:38 ` Kees Cook
2022-02-24 14:51 ` [PATCH v2 19/39] x86: Disable IBT around firmware Peter Zijlstra
2022-02-25 1:10 ` Kees Cook
2022-02-24 14:51 ` [PATCH v2 20/39] x86/bugs: Disable Retpoline when IBT Peter Zijlstra
2022-02-25 1:11 ` Kees Cook
2022-02-25 2:22 ` Josh Poimboeuf
2022-02-25 10:55 ` Peter Zijlstra
2022-02-24 14:51 ` [PATCH v2 21/39] x86/ibt: Annotate text references Peter Zijlstra
2022-02-25 0:47 ` Josh Poimboeuf
2022-02-25 12:57 ` Peter Zijlstra
2022-02-25 13:04 ` Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 22/39] x86/ibt,ftrace: Annotate ftrace code patching Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 23/39] x86/ibt,sev: Annotations Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 24/39] x86/text-patching: Make text_gen_insn() IBT aware Peter Zijlstra
2022-02-25 0:49 ` Josh Poimboeuf
2022-02-24 14:52 ` [PATCH v2 25/39] x86/ibt,paravirt: Use text_gen_insn() for paravirt_patch() Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 26/39] x86/entry: Cleanup PARAVIRT Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 27/39] x86/entry,xen: Early rewrite of restore_regs_and_return_to_kernel() Peter Zijlstra
2022-02-24 17:51 ` Andrew Cooper
2022-02-24 14:52 ` [PATCH v2 28/39] x86/ibt,xen: Sprinkle the ENDBR Peter Zijlstra
2022-02-25 0:54 ` Josh Poimboeuf
2022-02-25 13:16 ` Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 29/39] objtool: Rename --duplicate to --lto Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 30/39] Kbuild: Allow whole module objtool runs Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 31/39] objtool: Read the NOENDBR annotation Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 32/39] x86/ibt: Dont generate ENDBR in .discard.text Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 33/39] objtool: Add IBT/ENDBR decoding Peter Zijlstra
2022-03-03 10:53 ` Miroslav Benes
2022-03-03 11:06 ` Andrew Cooper
2022-03-03 12:33 ` Miroslav Benes
2022-03-03 14:13 ` Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 34/39] objtool: Validate IBT assumptions Peter Zijlstra
2022-02-27 3:13 ` Josh Poimboeuf
2022-02-27 17:00 ` Peter Zijlstra
2022-02-27 22:20 ` Josh Poimboeuf
2022-02-28 9:47 ` Peter Zijlstra
2022-02-28 18:36 ` Josh Poimboeuf
2022-02-28 20:10 ` Peter Zijlstra
2022-02-28 9:26 ` Peter Zijlstra
2022-02-28 18:39 ` Josh Poimboeuf
2022-02-24 14:52 ` [PATCH v2 35/39] objtool: IBT fix direct JMP/CALL Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 36/39] objtool: Find unused ENDBR instructions Peter Zijlstra
2022-02-27 3:46 ` Josh Poimboeuf
2022-02-28 12:41 ` Peter Zijlstra
2022-02-28 17:36 ` Josh Poimboeuf
2022-02-24 14:52 ` [PATCH v2 37/39] x86/ibt: Finish --ibt-fix-direct on module loading Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 38/39] x86/ibt: Ensure module init/exit points have references Peter Zijlstra
2022-02-24 14:52 ` [PATCH v2 39/39] x86/alternative: Use .ibt_endbr_sites to seal indirect calls Peter Zijlstra
2022-02-24 20:26 ` [PATCH v2 00/39] x86: Kernel IBT Josh Poimboeuf
2022-02-25 15:28 ` Peter Zijlstra
2022-02-25 15:43 ` Peter Zijlstra
2022-02-25 17:26 ` Josh Poimboeuf
2022-02-25 17:32 ` Steven Rostedt
2022-02-25 19:53 ` Peter Zijlstra
2022-02-25 20:15 ` Josh Poimboeuf
2022-03-01 23:10 ` Josh Poimboeuf
2022-03-02 10:20 ` Peter Zijlstra
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