Hi Nam,
On 19/11/2024 12:10, Nam Cao wrote:
p->ainsn.api.insn is a pointer to u32, therefore arithmetic operations are
multiplied by four. This is clearly undesirable for this case.
Cast it to (void *) first before any calculation.
Below is a sample before/after. The dumped memory is two kprobe slots, the
first slot has
- c.addiw a0, 0x1c (0x7125)
- ebreak (0x00100073)
and the second slot has:
- c.addiw a0, -4 (0x7135)
- ebreak (0x00100073)
Before this patch:
(gdb) x/16xh 0xff20000000135000
0xff20000000135000: 0x7125 0x0000 0x0000 0x0000 0x7135 0x0010 0x0000 0x0000
0xff20000000135010: 0x0073 0x0010 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
After this patch:
(gdb) x/16xh 0xff20000000125000
0xff20000000125000: 0x7125 0x0073 0x0010 0x0000 0x7135 0x0073 0x0010 0x0000
0xff20000000125010: 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
Fixes: b1756750a397 ("riscv: kprobes: Use patch_text_nosync() for insn slots")
Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
arch/riscv/kernel/probes/kprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 474a65213657..d2dacea1aedd 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -30,7 +30,7 @@ static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
p->ainsn.api.restore = (unsigned long)p->addr + len;
patch_text_nosync(p->ainsn.api.insn, &p->opcode, len);
- patch_text_nosync(p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(insn));
+ patch_text_nosync((void *)p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(insn));
}
static void __kprobes arch_prepare_simulate(struct kprobe *p)
This looks good to me, how did you find this issue?
You can add:
Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Thanks,
Alex
