The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 61119394631f219e23ce98bcc3eb993a64a8ea64 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024081917-flanked-clear-e564@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

61119394631f ("riscv: entry: always initialize regs->a0 to -ENOSYS") 05d450aabd73 ("riscv: Support RANDOMIZE_KSTACK_OFFSET")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 61119394631f219e23ce98bcc3eb993a64a8ea64 Mon Sep 17 00:00:00 2001 From: Celeste Liu coelacanthushex@gmail.com Date: Thu, 27 Jun 2024 22:23:39 +0800 Subject: [PATCH] riscv: entry: always initialize regs->a0 to -ENOSYS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

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

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).