This is a note to let you know that I've just added the patch titled
uprobes/x86: Allow to probe a NOP instruction with 0x66 prefix
to the 5.10-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:
uprobes-x86-allow-to-probe-a-nop-instruction-with-0x.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ff65b0284902b04ab9481b3183be40f27e3ed508
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
Date: Sun Dec 4 18:39:33 2022 +0100
uprobes/x86: Allow to probe a NOP instruction with 0x66 prefix
[ Upstream commit cefa72129e45313655d53a065b8055aaeb01a0c9 ]
Intel ICC -hotpatch inserts 2-byte "0x66 0x90" NOP at the start of each
function to reserve extra space for hot-patching, and currently it is not
possible to probe these functions because branch_setup_xol_ops() wrongly
rejects NOP with REP prefix as it treats them like word-sized branch
instructions.
Fixes: 250bbd12c2fe ("uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns")
Reported-by: Seiji Nishikawa <snishika@xxxxxxxxxx>
Suggested-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221204173933.GA31544@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 138bdb1fd136..9f948b2d26f6 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -722,8 +722,9 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
switch (opc1) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
- case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
break;
+ case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
+ goto setup;
case 0xe8: /* call relative */
branch_clear_offset(auprobe, insn);
@@ -753,6 +754,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
return -ENOTSUPP;
}
+setup:
auprobe->branch.opc1 = opc1;
auprobe->branch.ilen = insn->length;
auprobe->branch.offs = insn->immediate.value;
