This is a note to let you know that I've just added the patch titled
x86/kprobes: Fix optprobe optimization 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-optprobe-optimization-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 63dc6325ff41ee9e570bde705ac34a39c5dbeb44 Mon Sep 17 00:00:00 2001
From: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Date: Mon, 19 Dec 2022 23:35:19 +0900
Subject: x86/kprobes: Fix optprobe optimization check with CONFIG_RETHUNK
From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
commit 63dc6325ff41ee9e570bde705ac34a39c5dbeb44 upstream.
Since the CONFIG_RETHUNK and CONFIG_SLS will use INT3 for stopping
speculative execution after function return, kprobe jump optimization
always fails on the functions with such INT3 inside the function body.
(It already checks the INT3 padding between functions, but not inside
the function)
To avoid this issue, as same as kprobes, check whether the INT3 comes
from 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/167146051929.1374301.7419382929328081706.stgit@devnote3
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/kprobes/opt.c | 28 ++++++++--------------------
1 file changed, 8 insertions(+), 20 deletions(-)
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -15,6 +15,7 @@
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
+#include <linux/kgdb.h>
#include <linux/ftrace.h>
#include <linux/objtool.h>
#include <linux/pgtable.h>
@@ -279,19 +280,6 @@ static int insn_is_indirect_jump(struct
return ret;
}
-static bool is_padding_int3(unsigned long addr, unsigned long eaddr)
-{
- unsigned char ops;
-
- for (; addr < eaddr; addr++) {
- if (get_kernel_nofault(ops, (void *)addr) < 0 ||
- ops != INT3_INSN_OPCODE)
- return false;
- }
-
- return true;
-}
-
/* Decode whole function to ensure any instructions don't jump into target */
static int can_optimize(unsigned long paddr)
{
@@ -334,15 +322,15 @@ static int can_optimize(unsigned long pa
ret = insn_decode_kernel(&insn, (void *)recovered_insn);
if (ret < 0)
return 0;
-
+#ifdef CONFIG_KGDB
/*
- * In the case of detecting unknown breakpoint, this could be
- * a padding INT3 between functions. Let's check that all the
- * rest of the bytes are also INT3.
+ * If there is a dynamically installed kgdb sw breakpoint,
+ * this function should not be probed.
*/
- if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
- return is_padding_int3(addr, paddr - offset + size) ? 1 : 0;
-
+ if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
+ kgdb_has_hit_break(addr))
+ return 0;
+#endif
/* Recover address */
insn.kaddr = (void *)addr;
insn.next_byte = (void *)(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
