Close the hole where ptrace can change a syscall out from under seccomp.
Signed-off-by: Kees Cook <keesc...@chromium.org>
Cc: Jeff Dike <jd...@addtoit.com>
Cc: Richard Weinberger <rich...@nod.at>
Cc: user-mode-linux-de...@lists.sourceforge.net
---
arch/um/kernel/skas/syscall.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 9c5570f0f397..ef4b8f949b51 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -20,12 +20,12 @@ void handle_syscall(struct uml_pt_regs *r)
UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
- /* Do the secure computing check first; failures should be fast. */
- if (secure_computing(NULL) == -1)
+ if (syscall_trace_enter(regs))
return;
- if (syscall_trace_enter(regs))
- goto out;
+ /* Do the seccomp check after ptrace; failures should be fast. */
+ if (secure_computing(NULL) == -1)
+ return;
/* Update the syscall number after orig_ax has potentially been updated
* with ptrace.
@@ -37,6 +37,5 @@ void handle_syscall(struct uml_pt_regs *r)
PT_REGS_SET_SYSCALL_RETURN(regs,
EXECUTE_SYSCALL(syscall, regs));
-out:
syscall_trace_leave(regs);
}
--
2.7.4
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