On Thu, 16 Jun 2005, Michael Kerrisk wrote:
Regarding this bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=306517
I believe that the manual page probably correctly documents the
intended behaviour, but the implementation is wrong. In
fs/eventpoll.c::sys_epoll_ctl(), I believe the following:
error = -EFAULT;
if (EP_OP_HASH_EVENT(op) &&
copy_from_user(&epds, event, sizeof(struct epoll_event)))
goto eexit_1;
Should be guarded by something like
if (op != EPOLL_CTL_DEL)
But hopefully Davide (the implementer) can shed some light.
The code looks right to me. This is the EP_OP_HASH_EVENT() macro:
#define EP_OP_HASH_EVENT(op) ((op) != EPOLL_CTL_DEL)
If you call:
epoll_ctl(EPOLL_CTL_DEL, NULL);
you have that EP_OP_HASH_EVENT() is false, and hence the copy_from_user() in:
error = -EFAULT;
if (EP_OP_HASH_EVENT(op) &&
copy_from_user(&epds, event, sizeof(struct epoll_event)))
goto eexit_1;
is never executed. Has the bug report been run on recent kernels? That fix
is pretty old though, I think about a year old.
- Davide
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