From: Shu-Chun Weng <s...@google.com> Linux kernel does it this way (checks read permission before validating `how`) and the latest version of ABSL's `AddressIsReadable()` depends on this behavior.
c.f. https://github.com/torvalds/linux/blob/9539ba4308ad5bdca6cb41c7b73cbb9f796dcdd7/kernel/signal.c#L3147 Reviewed-by: Patrick Venture <vent...@google.com> Signed-off-by: Shu-Chun Weng <s...@google.com> Reviewed-by: Laurent Vivier <laur...@vivier.eu> Signed-off-by: Patrick Venture <vent...@google.com> --- linux-user/syscall.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 5950222a77..34bd819e38 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -9508,6 +9508,13 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1, } if (arg2) { + p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1); + if (!p) { + return -TARGET_EFAULT; + } + target_to_host_sigset(&set, p); + unlock_user(p, arg2, 0); + set_ptr = &set; switch(how) { case TARGET_SIG_BLOCK: how = SIG_BLOCK; @@ -9521,11 +9528,6 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1, default: return -TARGET_EINVAL; } - if (!(p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1))) - return -TARGET_EFAULT; - target_to_host_sigset(&set, p); - unlock_user(p, arg2, 0); - set_ptr = &set; } else { how = 0; set_ptr = NULL; -- 2.35.0.rc0.227.g00780c9af4-goog
