From f95a11a7daa7c29aa0a019b9c965bfdd6f3cb69a Mon Sep 17 00:00:00 2001 From: Daniel Bertalan Date: Wed, 11 Aug 2021 10:36:08 +0200 Subject: [PATCH] LibC: Don't delete null check in `gettimeofday` The `nonnull` attribute may delete null checks in the generated code, as per the [GCC documentation]: > The compiler may also perform optimizations based on the knowledge > that nonnul parameters cannot be null. This can currently not be > disabled other than by removing the nonnull attribute. Disassembling the function as compiled by GCC, we can see that there is no branch based on if `tv` is null. This means that `gettimeofday` would produce UB if passed a null parameter, even if we wanted to predictably return an error. Clang refuses to compile this due to a `pointer-bool-conversion` warning. In this commit, `settimeofday` is changed as well to match `gettimeofday`'s null argument handling. [GCC documentation]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-nonnull-function-attribute --- Userland/Libraries/LibC/sys/time.h | 4 ++-- Userland/Libraries/LibC/time.cpp | 5 +++++ 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/Userland/Libraries/LibC/sys/time.h b/Userland/Libraries/LibC/sys/time.h index 6d187e7ca4..7d670bfec8 100644 --- a/Userland/Libraries/LibC/sys/time.h +++ b/Userland/Libraries/LibC/sys/time.h @@ -23,8 +23,8 @@ struct timezone { }; int adjtime(const struct timeval* delta, struct timeval* old_delta); -int gettimeofday(struct timeval* __restrict__, void* __restrict__) __attribute__((nonnull(1))); -int settimeofday(struct timeval* __restrict__, void* __restrict__) __attribute__((nonnull(1))); +int gettimeofday(struct timeval* __restrict__, void* __restrict__); +int settimeofday(struct timeval* __restrict__, void* __restrict__); int utimes(const char* pathname, const struct timeval[2]); static inline void timeradd(const struct timeval* a, const struct timeval* b, struct timeval* out) diff --git a/Userland/Libraries/LibC/time.cpp b/Userland/Libraries/LibC/time.cpp index 016c966ee6..3cf77b7889 100644 --- a/Userland/Libraries/LibC/time.cpp +++ b/Userland/Libraries/LibC/time.cpp @@ -54,6 +54,11 @@ int gettimeofday(struct timeval* __restrict__ tv, void* __restrict__) int settimeofday(struct timeval* __restrict__ tv, void* __restrict__) { + if (!tv) { + errno = EFAULT; + return -1; + } + timespec ts; TIMEVAL_TO_TIMESPEC(tv, &ts); return clock_settime(CLOCK_REALTIME, &ts);