Commit fe4bfff8 authored by Kees Cook's avatar Kees Cook
Browse files

seccomp: Use -1 marker for end of mode 1 syscall list 



The terminator for the mode 1 syscalls list was a 0, but that could be
a valid syscall number (e.g. x86_64 __NR_read). By luck, __NR_read was
listed first and the loop construct would not test it, so there was no
bug. However, this is fragile. Replace the terminator with -1 instead,
and make the variable name for mode 1 syscall lists more descriptive.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 47e33c05

arch/mips/include/asm/seccomp.h

+2 −2
Original line number Diff line number Diff line
@@ -9,12 +9,12 @@ static inline const int *get_compat_mode1_syscalls(void) 
	static const int syscalls_O32[] = {

		__NR_O32_Linux + 3, __NR_O32_Linux + 4,

		__NR_O32_Linux + 1, __NR_O32_Linux + 193,

		0, /* null terminated */

		-1, /* negative terminated */

	};

	static const int syscalls_N32[] = {

		__NR_N32_Linux + 0, __NR_N32_Linux + 1,

		__NR_N32_Linux + 58, __NR_N32_Linux + 211,

		0, /* null terminated */

		-1, /* negative terminated */

	};



	if (IS_ENABLED(CONFIG_MIPS32_O32) && test_thread_flag(TIF_32BIT_REGS))

include/asm-generic/seccomp.h

+1 −1
Original line number Diff line number Diff line
@@ -33,7 +33,7 @@ static inline const int *get_compat_mode1_syscalls(void) 
	static const int mode1_syscalls_32[] = {

		__NR_seccomp_read_32, __NR_seccomp_write_32,

		__NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,

		0, /* null terminated */

		-1, /* negative terminated */

	};

	return mode1_syscalls_32;

}

kernel/seccomp.c

+5 −5
Original line number Diff line number Diff line
@@ -742,20 +742,20 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action, 
 */

static const int mode1_syscalls[] = {

	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,

	0, /* null terminated */

	-1, /* negative terminated */

};



static void __secure_computing_strict(int this_syscall)

{

	const int *syscall_whitelist = mode1_syscalls;

	const int *allowed_syscalls = mode1_syscalls;

#ifdef CONFIG_COMPAT

	if (in_compat_syscall())

		syscall_whitelist = get_compat_mode1_syscalls();

		allowed_syscalls = get_compat_mode1_syscalls();

#endif

	do {

		if (*syscall_whitelist == this_syscall)

		if (*allowed_syscalls == this_syscall)

			return;

	} while (*++syscall_whitelist);

	} while (*++allowed_syscalls != -1);



#ifdef SECCOMP_DEBUG

	dump_stack();

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