5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hanlin Song [ Upstream commit abb81e5ce7d995baa41556b8125fa59e28ba3be8 ] The syscall trace path reloads syscall arguments from pt_regs before calling the syscall handler. On C-SKY ABIv2, the 5th and 6th syscall arguments are prepared as stack arguments before invoking syscallid. The current code adjusts sp before loading LSAVE_A4 and LSAVE_A5. Since those offsets are relative to the original pt_regs base, loading them after changing sp fetches the wrong slots. As a result, traced syscalls that use the 5th or 6th argument may receive corrupted arguments. This is visible with mmap2(), which takes six arguments. A small PTRACE_SYSCALL reproducer opens a file and maps one page with: mmap(NULL, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0) Before the fix, the traced child fails the mmap and exits with 12. After the fix, the mapping succeeds and the child exits with 0. Fix the trace path by loading a4/a5 from pt_regs before changing sp. Tested on: ck860f, linux-4.19.15, C-SKY abiv2 Fixes: e0bbb53843b5 ("csky: Fixup abiv2 syscall_trace break a4 & a5") Suggested-by: Guo Ren Signed-off-by: Hanlin Song Signed-off-by: Guo Ren (Alibaba DAMO Academy) Signed-off-by: Sasha Levin --- arch/csky/kernel/entry.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S index 5a5cabd076e16..6a9e0d304d2c5 100644 --- a/arch/csky/kernel/entry.S +++ b/arch/csky/kernel/entry.S @@ -196,11 +196,11 @@ csky_syscall_trace: ldw a2, (sp, LSAVE_A2) ldw a3, (sp, LSAVE_A3) #if defined(__CSKYABIV2__) - subi sp, 8 ldw r9, (sp, LSAVE_A4) + ldw r10, (sp, LSAVE_A5) + subi sp, 8 stw r9, (sp, 0x0) - ldw r9, (sp, LSAVE_A5) - stw r9, (sp, 0x4) + stw r10, (sp, 0x4) jsr syscallid /* Do system call */ addi sp, 8 #else -- 2.53.0