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From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Kees Cook" <keescook@chromium.org>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Richard Weinberger" <richard@nod.at>,
	"James Morris" <jmorris@namei.org>,
	"Olof Johansson" <olof@lixom.net>,
	user-mode-linux-devel@lists.sourceforge.net,
	linux-security-module@vger.kernel.org
Subject: [PATCH v2 2/3] um/ptrace: Fix the syscall number update after a ptrace
Date: Mon,  1 Aug 2016 23:01:56 +0200
Message-ID: <1470085317-11932-3-git-send-email-mic@digikod.net> (raw)
In-Reply-To: <1470085317-11932-1-git-send-email-mic@digikod.net>

Update the syscall number after each PTRACE_SETREGS on ORIG_*AX.

This is needed to get the potentially altered syscall number in the
seccomp filters after RET_TRACE.

This fix four seccomp_bpf tests:
> [ RUN      ] TRACE_syscall.skip_after_RET_TRACE
> seccomp_bpf.c:1560:TRACE_syscall.skip_after_RET_TRACE:Expected -1 (18446744073709551615) == syscall(39) (26)
> seccomp_bpf.c:1561:TRACE_syscall.skip_after_RET_TRACE:Expected 1 (1) == (*__errno_location ()) (22)
> [     FAIL ] TRACE_syscall.skip_after_RET_TRACE
> [ RUN      ] TRACE_syscall.kill_after_RET_TRACE
> TRACE_syscall.kill_after_RET_TRACE: Test exited normally instead of by signal (code: 1)
> [     FAIL ] TRACE_syscall.kill_after_RET_TRACE
> [ RUN      ] TRACE_syscall.skip_after_ptrace
> seccomp_bpf.c:1622:TRACE_syscall.skip_after_ptrace:Expected -1 (18446744073709551615) == syscall(39) (26)
> seccomp_bpf.c:1623:TRACE_syscall.skip_after_ptrace:Expected 1 (1) == (*__errno_location ()) (22)
> [     FAIL ] TRACE_syscall.skip_after_ptrace
> [ RUN      ] TRACE_syscall.kill_after_ptrace
> TRACE_syscall.kill_after_ptrace: Test exited normally instead of by signal (code: 1)
> [     FAIL ] TRACE_syscall.kill_after_ptrace

Fixes: 26703c636c1f ("um/ptrace: run seccomp after ptrace")

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: James Morris <jmorris@namei.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
---
 arch/um/kernel/skas/syscall.c | 5 -----
 arch/x86/um/ptrace_32.c       | 3 +++
 arch/x86/um/ptrace_64.c       | 4 ++++
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 0728fee94398..b783ac87d98a 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -27,12 +27,7 @@ void handle_syscall(struct uml_pt_regs *r)
 	if (secure_computing(NULL) == -1)
 		goto out;
 
-	/* Update the syscall number after orig_ax has potentially been updated
-	 * with ptrace.
-	 */
-	UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
 	syscall = UPT_SYSCALL_NR(r);
-
 	if (syscall >= 0 && syscall <= __NR_syscall_max)
 		PT_REGS_SET_SYSCALL_RETURN(regs,
 				EXECUTE_SYSCALL(syscall, regs));
diff --git a/arch/x86/um/ptrace_32.c b/arch/x86/um/ptrace_32.c
index ebd4dd6ef73b..a7ef7b131e25 100644
--- a/arch/x86/um/ptrace_32.c
+++ b/arch/x86/um/ptrace_32.c
@@ -84,7 +84,10 @@ int putreg(struct task_struct *child, int regno, unsigned long value)
 	case EAX:
 	case EIP:
 	case UESP:
+		break;
 	case ORIG_EAX:
+		/* Update the syscall number. */
+		UPT_SYSCALL_NR(&child->thread.regs.regs) = value;
 		break;
 	case FS:
 		if (value && (value & 3) != 3)
diff --git a/arch/x86/um/ptrace_64.c b/arch/x86/um/ptrace_64.c
index faab418876ce..0b5c184dd5b3 100644
--- a/arch/x86/um/ptrace_64.c
+++ b/arch/x86/um/ptrace_64.c
@@ -78,7 +78,11 @@ int putreg(struct task_struct *child, int regno, unsigned long value)
 	case RSI:
 	case RDI:
 	case RBP:
+		break;
+
 	case ORIG_RAX:
+		/* Update the syscall number. */
+		UPT_SYSCALL_NR(&child->thread.regs.regs) = value;
 		break;
 
 	case FS:
-- 
2.8.1

  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-11 21:56 [PATCH v1 0/3] Fix seccomp for UM (next) Mickaël Salaün
2016-07-11 21:57 ` [PATCH v1 1/3] um/ptrace: Fix the syscall_trace_leave call Mickaël Salaün
2016-07-11 21:57 ` [PATCH v1 2/3] um/ptrace: Fix the syscall number update after a ptrace Mickaël Salaün
2016-07-11 21:57 ` [PATCH v1 3/3] seccomp: Remove 2-phase API documentation Mickaël Salaün
2016-07-12  1:59 ` [PATCH v1 0/3] Fix seccomp for UM (next) Kees Cook
2016-07-28 18:29   ` Kees Cook
2016-08-01  0:54     ` James Morris
2016-08-01 21:01       ` [PATCH v2 " Mickaël Salaün
2016-08-01 21:01         ` [PATCH v2 1/3] um/ptrace: Fix the syscall_trace_leave call Mickaël Salaün
2016-08-01 21:01         ` Mickaël Salaün [this message]
2016-08-01 21:01         ` [PATCH v2 3/3] seccomp: Remove 2-phase API documentation Mickaël Salaün
2016-08-09  0:35         ` [PATCH v2 0/3] Fix seccomp for UM (next) James Morris
2016-09-06 20:31           ` [PATCH v2 0/3] Fix seccomp for UM Mickaël Salaün

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