diff options
| -rw-r--r-- | arch/x86/kernel/signal_compat.c | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index 5335ad96a290..b44564bf86a8 100644 --- a/arch/x86/kernel/signal_compat.c +++ b/arch/x86/kernel/signal_compat.c @@ -1,11 +1,104 @@ #include <linux/compat.h> #include <linux/uaccess.h> +/* + * The compat_siginfo_t structure and handing code is very easy + * to break in several ways. It must always be updated when new + * updates are made to the main siginfo_t, and + * copy_siginfo_to_user32() must be updated when the + * (arch-independent) copy_siginfo_to_user() is updated. + * + * It is also easy to put a new member in the compat_siginfo_t + * which has implicit alignment which can move internal structure + * alignment around breaking the ABI. This can happen if you, + * for instance, put a plain 64-bit value in there. + */ +static inline void signal_compat_build_tests(void) +{ + int _sifields_offset = offsetof(compat_siginfo_t, _sifields); + + /* + * If adding a new si_code, there is probably new data in + * the siginfo. Make sure folks bumping the si_code + * limits also have to look at this code. Make sure any + * new fields are handled in copy_siginfo_to_user32()! + */ + BUILD_BUG_ON(NSIGILL != 8); + BUILD_BUG_ON(NSIGFPE != 8); + BUILD_BUG_ON(NSIGSEGV != 4); + BUILD_BUG_ON(NSIGBUS != 5); + BUILD_BUG_ON(NSIGTRAP != 4); + BUILD_BUG_ON(NSIGCHLD != 6); + BUILD_BUG_ON(NSIGSYS != 1); + + /* This is part of the ABI and can never change in size: */ + BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128); + /* + * The offsets of all the (unioned) si_fields are fixed + * in the ABI, of course. Make sure none of them ever + * move and are always at the beginning: + */ + BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int)); +#define CHECK_CSI_OFFSET(name) BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name)) + + /* + * Ensure that the size of each si_field never changes. + * If it does, it is a sign that the + * copy_siginfo_to_user32() code below needs to updated + * along with the size in the CHECK_SI_SIZE(). + * + * We repeat this check for both the generic and compat + * siginfos. + * + * Note: it is OK for these to grow as long as the whole + * structure stays within the padding size (checked + * above). + */ +#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name)) +#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name)) + + CHECK_CSI_OFFSET(_kill); + CHECK_CSI_SIZE (_kill, 2*sizeof(int)); + CHECK_SI_SIZE (_kill, 2*sizeof(int)); + + CHECK_CSI_OFFSET(_timer); + CHECK_CSI_SIZE (_timer, 5*sizeof(int)); + CHECK_SI_SIZE (_timer, 6*sizeof(int)); + + CHECK_CSI_OFFSET(_rt); + CHECK_CSI_SIZE (_rt, 3*sizeof(int)); + CHECK_SI_SIZE (_rt, 4*sizeof(int)); + + CHECK_CSI_OFFSET(_sigchld); + CHECK_CSI_SIZE (_sigchld, 5*sizeof(int)); + CHECK_SI_SIZE (_sigchld, 8*sizeof(int)); + + CHECK_CSI_OFFSET(_sigchld_x32); + CHECK_CSI_SIZE (_sigchld_x32, 7*sizeof(int)); + /* no _sigchld_x32 in the generic siginfo_t */ + + CHECK_CSI_OFFSET(_sigfault); + CHECK_CSI_SIZE (_sigfault, 4*sizeof(int)); + CHECK_SI_SIZE (_sigfault, 8*sizeof(int)); + + CHECK_CSI_OFFSET(_sigpoll); + CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int)); + CHECK_SI_SIZE (_sigpoll, 4*sizeof(int)); + + CHECK_CSI_OFFSET(_sigsys); + CHECK_CSI_SIZE (_sigsys, 3*sizeof(int)); + CHECK_SI_SIZE (_sigsys, 4*sizeof(int)); + + /* any new si_fields should be added here */ +} + int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from) { int err = 0; bool ia32 = test_thread_flag(TIF_IA32); + signal_compat_build_tests(); + if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t))) return -EFAULT; |