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| author | Martin Kaiser <martin@kaiser.cx> | 2026-06-30 21:40:03 +0200 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2026-06-30 18:46:54 -0600 |
| commit | bc7b086a45521a986a49045907f017e3e46c763e (patch) | |
| tree | 111947c304a4ce82e8f5ae9f923674b57b803526 | |
| parent | c4c7756a81b5baef286bf9be1ea404f3e4dd7a3c (diff) | |
| download | linux-next-bc7b086a45521a986a49045907f017e3e46c763e.tar.gz linux-next-bc7b086a45521a986a49045907f017e3e46c763e.zip | |
riscv: probes: save original sp in rethook trampoline
Reading a word from the stack in a kretprobe crashes a risc-v kernel.
$ cd /sys/kernel/tracing/
$ echo 'r n_tty_write $stack0' > dynamic_events
$ echo 1 > events/kprobes/enable
Unable to handle kernel paging request at virtual address 0000000200000128
...
[<ffffffff80016d16>] regs_get_kernel_stack_nth+0x26/0x38
[<ffffffff80177196>] process_fetch_insn+0x3ee/0x760
[<ffffffff80177836>] kretprobe_trace_func+0x116/0x1f0
[<ffffffff8017795a>] kretprobe_dispatcher+0x4a/0x58
[<ffffffff8013572e>] kretprobe_rethook_handler+0x5e/0x90
[<ffffffff80180838>] rethook_trampoline_handler+0x70/0x108
[<ffffffff8001ba32>] arch_rethook_trampoline_callback+0x12/0x1c
[<ffffffff8001ba84>] arch_rethook_trampoline+0x48/0x94
[<ffffffff8067872a>] tty_write+0x1a/0x30
In regs_get_kernel_stack_nth, regs->sp contains an arbitrary value.
arch_rethook_trampoline saves the registers from the probed function in a
struct pt_regs. sp is not saved. Instead, sp is decremented for
arch_rethook_trampoline's local stack.
Fix this crash and save the original sp along with the other registers.
Use a0 as a temporary register, it is overwritten anyway.
Cc: stable@vger.kernel.org
Fixes: c22b0bcb1dd02 ("riscv: Add kprobes supported")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://patch.msgid.link/20260630194010.1824039-1-martin@kaiser.cx
[pjw@kernel.org: added Fixes tag; cc'ed stable]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
| -rw-r--r-- | arch/riscv/kernel/probes/rethook_trampoline.S | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/riscv/kernel/probes/rethook_trampoline.S b/arch/riscv/kernel/probes/rethook_trampoline.S index f2cd83d9b0f0..c3aa8d8cf5af 100644 --- a/arch/riscv/kernel/probes/rethook_trampoline.S +++ b/arch/riscv/kernel/probes/rethook_trampoline.S @@ -41,6 +41,9 @@ REG_S x29, PT_T4(sp) REG_S x30, PT_T5(sp) REG_S x31, PT_T6(sp) + /* save original sp */ + addi a0, sp, PT_SIZE_ON_STACK + REG_S a0, PT_SP(sp) .endm .macro restore_all_base_regs |