From de8cd0dc834f2294bcf20240ea037c3864bc4f9a Mon Sep 17 00:00:00 2001 From: James Hogan Date: Fri, 11 Aug 2017 21:56:52 +0100 Subject: MIPS/ptrace: Update syscall nr on register changes Update the thread_info::syscall field when registers are modified via ptrace to change or cancel the system call being entered. This is important to allow seccomp and the syscall entry and exit trace events to observe the new syscall number changed by the normal ptrace hook or seccomp. That includes allowing seccomp's recheck of the system call number after SECCOMP_RET_TRACE to notice if the syscall is changed to a denied one, which happens in seccomp since commit ce6526e8afa4 ("seccomp: recheck the syscall after RET_TRACE") in v4.8. In the process of doing this, the logic to determine whether an indirect system call is in progress (i.e. the O32 ABI's syscall()) is abstracted into mips_syscall_is_indirect(), and a new mips_syscall_update_nr() is used to update the thread_info::syscall based on the register state. The following ptrace operations are updated: - PTRACE_SETREGS (ptrace_setregs()). - PTRACE_SETREGSET with NT_PRSTATUS (gpr32_set() and gpr64_set()). - PTRACE_POKEUSR with 2/v0 or 4/a0 for indirect syscall ([compat_]arch_ptrace()). Fixes: c2d9f1775731 ("MIPS: Fix syscall_get_nr for the syscall exit tracing.") Signed-off-by: James Hogan Cc: Ralf Baechle Cc: Lars Persson Cc: Oleg Nesterov Cc: Kees Cook Cc: Andy Lutomirski Cc: Will Drewry Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16995/ --- arch/mips/kernel/ptrace.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'arch/mips/kernel/ptrace.c') diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c index 011993e0cce2..efbd8df8b665 100644 --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -144,6 +144,9 @@ int ptrace_setregs(struct task_struct *child, struct user_pt_regs __user *data) /* badvaddr, status, and cause may not be written. */ + /* System call number may have been changed */ + mips_syscall_update_nr(child, regs); + return 0; } @@ -345,6 +348,9 @@ static int gpr32_set(struct task_struct *target, } } + /* System call number may have been changed */ + mips_syscall_update_nr(target, regs); + return 0; } @@ -405,6 +411,9 @@ static int gpr64_set(struct task_struct *target, } } + /* System call number may have been changed */ + mips_syscall_update_nr(target, regs); + return 0; } @@ -770,6 +779,12 @@ long arch_ptrace(struct task_struct *child, long request, switch (addr) { case 0 ... 31: regs->regs[addr] = data; + /* System call number may have been changed */ + if (addr == 2) + mips_syscall_update_nr(child, regs); + else if (addr == 4 && + mips_syscall_is_indirect(child, regs)) + mips_syscall_update_nr(child, regs); break; case FPR_BASE ... FPR_BASE + 31: { union fpureg *fregs = get_fpu_regs(child); -- cgit