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

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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: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-06-19 12:20:15 -07:00
parent 47e33c05f9
commit fe4bfff86e
3 changed files with 8 additions and 8 deletions
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4
arch/mips/include/asm/seccomp.h
View File

@ -9,12 +9,12 @@ static inline const int *get_compat_mode1_syscalls(void)
static const int syscalls_O32[] = { static const int syscalls_O32[] = {
__NR_O32_Linux + 3, __NR_O32_Linux + 4, __NR_O32_Linux + 3, __NR_O32_Linux + 4,
__NR_O32_Linux + 1, __NR_O32_Linux + 193, __NR_O32_Linux + 1, __NR_O32_Linux + 193,
0, /* null terminated */ -1, /* negative terminated */
}; };
static const int syscalls_N32[] = { static const int syscalls_N32[] = {
__NR_N32_Linux + 0, __NR_N32_Linux + 1, __NR_N32_Linux + 0, __NR_N32_Linux + 1,
__NR_N32_Linux + 58, __NR_N32_Linux + 211, __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)) if (IS_ENABLED(CONFIG_MIPS32_O32) && test_thread_flag(TIF_32BIT_REGS))

2
include/asm-generic/seccomp.h
View File

@ -33,7 +33,7 @@ static inline const int *get_compat_mode1_syscalls(void)
static const int mode1_syscalls_32[] = { static const int mode1_syscalls_32[] = {
__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_read_32, __NR_seccomp_write_32,
__NR_seccomp_exit_32, __NR_seccomp_sigreturn_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
0, /* null terminated */ -1, /* negative terminated */
}; };
return mode1_syscalls_32; return mode1_syscalls_32;
} }

10
kernel/seccomp.c
View File

@ -742,20 +742,20 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
*/ */
static const int mode1_syscalls[] = { static const int mode1_syscalls[] = {
__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, __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) static void __secure_computing_strict(int this_syscall)
{ {
const int *syscall_whitelist = mode1_syscalls; const int *allowed_syscalls = mode1_syscalls;
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
if (in_compat_syscall()) if (in_compat_syscall())
syscall_whitelist = get_compat_mode1_syscalls(); allowed_syscalls = get_compat_mode1_syscalls();
#endif #endif
do { do {
if (*syscall_whitelist == this_syscall) if (*allowed_syscalls == this_syscall)
return; return;
} while (*++syscall_whitelist); } while (*++allowed_syscalls != -1);
#ifdef SECCOMP_DEBUG #ifdef SECCOMP_DEBUG
dump_stack(); dump_stack();