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authorCeleste Liu <coelacanthushex@gmail.com>2024-06-27 22:23:39 +0800
committerPalmer Dabbelt <palmer@rivosinc.com>2024-08-14 13:12:22 -0700
commit61119394631f219e23ce98bcc3eb993a64a8ea64 (patch)
treeb0b47a1e641edcb5eff2b050813872501dc5b8c9 /arch
parentee9a68394b4bea8b9044ec4bfdbaacf45297ecef (diff)
riscv: entry: always initialize regs->a0 to -ENOSYS
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") Reported-by: "Dmitry V. Levin" <ldv@strace.io> Reviewed-by: Björn Töpel <bjorn@rivosinc.com> Cc: stable@vger.kernel.org Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> Link: https://lore.kernel.org/r/20240627142338.5114-2-CoelacanthusHex@gmail.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/riscv/kernel/traps.c4
1 files changed, 2 insertions, 2 deletions
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).