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epoll_ctl warns for uninitialized padding on non-amd64 64bit arches

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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
This commit is contained in:
Mark Wielaard
2020-07-26 22:40:22 +02:00
parent 6323fd5bfd
commit ecf5ba1197
2 changed files with 28 additions and 8 deletions
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1
NEWS
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@@ -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.

35
coregrind/m_syswrap/syswrap-linux.c
View File

@@ -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)