Ensure the futex value fits in the given futex size. Since this adds a constraint to an existing syscall, it might possibly change behaviour. Currently the value would be truncated to a u32 and any high bits would get silently lost. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner --- kernel/futex/futex.h | 10 ++++++++++ kernel/futex/syscalls.c | 3 +++ 2 files changed, 13 insertions(+) Index: linux-2.6/kernel/futex/futex.h =================================================================== --- linux-2.6.orig/kernel/futex/futex.h +++ linux-2.6/kernel/futex/futex.h @@ -85,6 +85,16 @@ static inline bool futex_flags_valid(uns return true; } +static inline bool futex_validate_input(unsigned int flags, u64 val) +{ + int bits = 8 * futex_size(flags); + + if (bits < 64 && (val >> bits)) + return false; + + return true; +} + #ifdef CONFIG_FAIL_FUTEX extern bool should_fail_futex(bool fshared); #else Index: linux-2.6/kernel/futex/syscalls.c =================================================================== --- linux-2.6.orig/kernel/futex/syscalls.c +++ linux-2.6/kernel/futex/syscalls.c @@ -209,6 +209,9 @@ static int futex_parse_waitv(struct fute if (!futex_flags_valid(flags)) return -EINVAL; + if (!futex_validate_input(flags, aux.val)) + return -EINVAL; + futexv[i].w.flags = flags; futexv[i].w.val = aux.val; futexv[i].w.uaddr = aux.uaddr;