Messages in this thread | | | Subject | Re: [PATCH v5] riscv: entry: set a0 = -ENOSYS only when syscall != -1 | From | patchwork-bot+linux-riscv@kernel ... | Date | Thu, 17 Aug 2023 15:20:24 +0000 |
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Hello:
This patch was applied to riscv/linux.git (fixes) by Palmer Dabbelt <palmer@rivosinc.com>:
On Tue, 1 Aug 2023 22:15:16 +0800 you wrote: > When we test seccomp with 6.4 kernel, we found errno has wrong value. > If we deny NETLINK_AUDIT with EAFNOSUPPORT, after f0bddf50586d, we will > get ENOSYS instead. We got same result with commit 9c2598d43510 ("riscv: > entry: Save a0 prior syscall_enter_from_user_mode()"). > > After analysing code, we think that regs->a0 = -ENOSYS should only be > executed when syscall != -1. In __seccomp_filter, when seccomp rejected > this syscall with specified errno, they will set a0 to return number as > syscall ABI, and then return -1. This return number is finally pass as > return number of syscall_enter_from_user_mode, and then is compared with > NR_syscalls after converted to ulong (so it will be ULONG_MAX). The > condition syscall < NR_syscalls will always be false, so regs->a0 = -ENOSYS > is always executed. It covered a0 set by seccomp, so we always get > ENOSYS when match seccomp RET_ERRNO rule. > > [...]
Here is the summary with links: - [v5] riscv: entry: set a0 = -ENOSYS only when syscall != -1 https://git.kernel.org/riscv/c/52449c17bdd1
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