| Message ID | 20240627103205.27914-2-CoelacanthusHex@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | riscv: entry: always initialize regs->a0 to -ENOSYS | expand |
Celeste Liu <coelacanthushex@gmail.com> writes: > Otherwise when the tracer changes syscall number to -1, the kernel fails > to initialize a0 with -ENOSYS and subsequently fails to return the error > code of the failed syscall to userspace. For example, it will break > strace syscall tampering. > > Fixes: 52449c17bdd1 ("riscv: entry: set a0 = -ENOSYS only when syscall != -1") > Cc: stable@vger.kernel.org > Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> Reported-by: "Dmitry V. Levin" <ldv@strace.io> Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
On 2024-06-27 22:08, Björn Töpel wrote: > Celeste Liu <coelacanthushex@gmail.com> writes: > >> Otherwise when the tracer changes syscall number to -1, the kernel fails >> to initialize a0 with -ENOSYS and subsequently fails to return the error >> code of the failed syscall to userspace. For example, it will break >> strace syscall tampering. >> >> Fixes: 52449c17bdd1 ("riscv: entry: set a0 = -ENOSYS only when syscall != -1") >> Cc: stable@vger.kernel.org >> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> > > Reported-by: "Dmitry V. Levin" <ldv@strace.io> > Reviewed-by: Björn Töpel <bjorn@rivosinc.com> Patch v2 has been sent.
On Thu, 27 Jun 2024 at 16:29, Celeste Liu <coelacanthushex@gmail.com> wrote: > > On 2024-06-27 22:08, Björn Töpel wrote: > > > Celeste Liu <coelacanthushex@gmail.com> writes: > > > >> Otherwise when the tracer changes syscall number to -1, the kernel fails > >> to initialize a0 with -ENOSYS and subsequently fails to return the error > >> code of the failed syscall to userspace. For example, it will break > >> strace syscall tampering. > >> > >> Fixes: 52449c17bdd1 ("riscv: entry: set a0 = -ENOSYS only when syscall != -1") > >> Cc: stable@vger.kernel.org > >> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> > > > > Reported-by: "Dmitry V. Levin" <ldv@strace.io> > > Reviewed-by: Björn Töpel <bjorn@rivosinc.com> > > Patch v2 has been sent. For future patches; You don't need to respin a patch to add tags. The tooling will pick up the tags automatically.
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 05a16b1f0aee..51ebfd23e007 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -319,6 +319,7 @@ void do_trap_ecall_u(struct pt_regs *regs) regs->epc += 4; regs->orig_a0 = regs->a0; + regs->a0 = -ENOSYS; riscv_v_vstate_discard(regs); @@ -328,8 +329,7 @@ void do_trap_ecall_u(struct pt_regs *regs) if (syscall >= 0 && syscall < NR_syscalls) syscall_handler(regs, syscall); - else if (syscall != -1) - regs->a0 = -ENOSYS; + /* * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(), * so the maximum stack offset is 1k bytes (10 bits).
Otherwise when the tracer changes syscall number to -1, the kernel fails to initialize a0 with -ENOSYS and subsequently fails to return the error code of the failed syscall to userspace. For example, it will break strace syscall tampering. Fixes: 52449c17bdd1 ("riscv: entry: set a0 = -ENOSYS only when syscall != -1") Cc: stable@vger.kernel.org Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> --- arch/riscv/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)