This is a note to let you know that I've just added the patch titled
x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-kprobes-fix-kprobes-instruction-boudary-check-with-config_rethunk.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1993bf97992df2d560287f3c4120eda57426843d Mon Sep 17 00:00:00 2001
From: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Date: Mon, 19 Dec 2022 23:35:10 +0900
Subject: x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK
From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
commit 1993bf97992df2d560287f3c4120eda57426843d upstream.
Since the CONFIG_RETHUNK and CONFIG_SLS will use INT3 for stopping
speculative execution after RET instruction, kprobes always failes to
check the probed instruction boundary by decoding the function body if
the probed address is after such sequence. (Note that some conditional
code blocks will be placed after function return, if compiler decides
it is not on the hot path.)
This is because kprobes expects kgdb puts the INT3 as a software
breakpoint and it will replace the original instruction.
But these INT3 are not such purpose, it doesn't need to recover the
original instruction.
To avoid this issue, kprobes checks whether the INT3 is owned by
kgdb or not, and if so, stop decoding and make it fail. The other
INT3 will come from CONFIG_RETHUNK/CONFIG_SLS and those can be
treated as a one-byte instruction.
Fixes: e463a09af2f0 ("x86: Add straight-line-speculation mitigation")
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/167146051026.1374301.392728975473572291.stgit@devnote3
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/kprobes/core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -37,6 +37,7 @@
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
+#include <linux/kgdb.h>
#include <linux/ftrace.h>
#include <linux/kasan.h>
#include <linux/moduleloader.h>
@@ -281,12 +282,15 @@ static int can_probe(unsigned long paddr
if (ret < 0)
return 0;
+#ifdef CONFIG_KGDB
/*
- * Another debugging subsystem might insert this breakpoint.
- * In that case, we can't recover it.
+ * If there is a dynamically installed kgdb sw breakpoint,
+ * this function should not be probed.
*/
- if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
+ if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
+ kgdb_has_hit_break(addr))
return 0;
+#endif
addr += insn.length;
}
Patches currently in stable-queue which might be from mhiramat@xxxxxxxxxx are
queue-6.1/tracing-fix-race-where-eprobes-can-be-called-before-the-event.patch
queue-6.1/x86-kprobes-fix-optprobe-optimization-check-with-config_rethunk.patch
queue-6.1/tracing-fix-issue-of-missing-one-synthetic-field.patch
queue-6.1/arm64-prohibit-instrumentation-on-arch_stack_walk.patch
queue-6.1/tracing-hist-fix-wrong-return-value-in-parse_action_params.patch
queue-6.1/tracing-probes-handle-system-names-with-hyphens.patch
queue-6.1/tracing-hist-fix-out-of-bound-write-on-action_data.var_ref_idx.patch
queue-6.1/x86-kprobes-fix-kprobes-instruction-boudary-check-with-config_rethunk.patch
queue-6.1/tracing-fix-complicated-dependency-of-config_tracer_max_trace.patch
queue-6.1/tracing-fix-infinite-loop-in-tracing_read_pipe-on-overflowed-print_trace_line.patch
queue-6.1/ftrace-x86-add-back-ftrace_expected-for-ftrace-bug-reports.patch
