From ecf5ba1197c3833759b40712c401f0bdc768589f Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Sun, 26 Jul 2020 22:40:22 +0200 Subject: [PATCH] epoll_ctl warns for uninitialized padding on non-amd64 64bit arches struct vki_epoll_event is packed on x86_64, but not on other 64bit arches. This means that on 64bit arches there can be padding in the epoll_event struct. Seperately the data field is only used by user space (which might not set the data field if it doesn't need to). Only check the events field on epoll_ctl. But assume both events and data are both written to by epoll_[p]wait (exclude padding). https://bugs.kde.org/show_bug.cgi?id=422623 --- NEWS | 1 + coregrind/m_syswrap/syswrap-linux.c | 35 ++++++++++++++++++++++------- 2 files changed, 28 insertions(+), 8 deletions(-) diff --git a/NEWS b/NEWS index 77de28a294..976344cdc0 100644 --- a/NEWS +++ b/NEWS @@ -43,6 +43,7 @@ where XXXXXX is the bug number as listed below. 369029 handle linux syscalls sched_getattr and sched_setattr n-i-bz helgrind: If hg_cli__realloc fails, return NULL. +422623 epoll_ctl warns for uninitialized padding on non-amd64 64bit arches 423021 PPC: Add missing ISA 3.0 documentation link and HWCAPS test. diff --git a/coregrind/m_syswrap/syswrap-linux.c b/coregrind/m_syswrap/syswrap-linux.c index 56be3032d3..dd41022108 100644 --- a/coregrind/m_syswrap/syswrap-linux.c +++ b/coregrind/m_syswrap/syswrap-linux.c @@ -2099,8 +2099,29 @@ PRE(sys_epoll_ctl) SARG1, ( ARG2<3 ? epoll_ctl_s[ARG2] : "?" ), SARG3, ARG4); PRE_REG_READ4(long, "epoll_ctl", int, epfd, int, op, int, fd, struct vki_epoll_event *, event); - if (ARG2 != VKI_EPOLL_CTL_DEL) - PRE_MEM_READ( "epoll_ctl(event)", ARG4, sizeof(struct vki_epoll_event) ); + if (ARG2 != VKI_EPOLL_CTL_DEL) { + /* Just check the events field, the data field is for user space and + unused by the kernel. */ + struct vki_epoll_event *event = (struct vki_epoll_event *) ARG4; + PRE_MEM_READ( "epoll_ctl(event)", (Addr) &event->events, + sizeof(__vki_u32) ); + } +} + +/* RES event records have been written (exclude padding). */ +static void epoll_post_helper ( ThreadId tid, SyscallArgs* arrghs, + SyscallStatus* status ) +{ + vg_assert(SUCCESS); + if (RES > 0) { + Int i; + struct vki_epoll_event **events = (struct vki_epoll_event**)(Addr)ARG2; + for (i = 0; i < RES; i++) { + /* Assume both events and data are set (data is user space only). */ + POST_FIELD_WRITE(events[i]->events); + POST_FIELD_WRITE(events[i]->data); + } + } } PRE(sys_epoll_wait) @@ -2111,13 +2132,12 @@ PRE(sys_epoll_wait) PRE_REG_READ4(long, "epoll_wait", int, epfd, struct vki_epoll_event *, events, int, maxevents, int, timeout); + /* Assume all (maxevents) events records should be (fully) writable. */ PRE_MEM_WRITE( "epoll_wait(events)", ARG2, sizeof(struct vki_epoll_event)*ARG3); } POST(sys_epoll_wait) { - vg_assert(SUCCESS); - if (RES > 0) - POST_MEM_WRITE( ARG2, sizeof(struct vki_epoll_event)*RES ) ; + epoll_post_helper (tid, arrghs, status); } PRE(sys_epoll_pwait) @@ -2130,15 +2150,14 @@ PRE(sys_epoll_pwait) int, epfd, struct vki_epoll_event *, events, int, maxevents, int, timeout, vki_sigset_t *, sigmask, vki_size_t, sigsetsize); + /* Assume all (maxevents) events records should be (fully) writable. */ PRE_MEM_WRITE( "epoll_pwait(events)", ARG2, sizeof(struct vki_epoll_event)*ARG3); if (ARG5) PRE_MEM_READ( "epoll_pwait(sigmask)", ARG5, sizeof(vki_sigset_t) ); } POST(sys_epoll_pwait) { - vg_assert(SUCCESS); - if (RES > 0) - POST_MEM_WRITE( ARG2, sizeof(struct vki_epoll_event)*RES ) ; + epoll_post_helper (tid, arrghs, status); } PRE(sys_eventfd) -- 2.47.2