Back about a year ago when I last fiddled heavily with the do_wait code, I
was thinking too hard about the wrong thing and I now think I introduced a
bug whose inverse thought I was fixing. Apparently noone was looking too
hard over much shoulder, so as to cite my bogus reasoning at the time. In
the race condition when PTRACE_ATTACH is about to steal a child and then
the child hits a tracing event (what my_ptrace_child checks for), the real
parent does need to set its flag noting it has some eligible live children.
Otherwise a spurious ECHILD error is possible, since the child in question
is not yet on the ptrace_children list.
Signed-off-by: Roland McGrath <[email protected]>
--- linux-2.6/kernel/exit.c
+++ linux-2.6/kernel/exit.c
@@ -1370,6 +1370,15 @@ repeat:
switch (p->state) {
case TASK_TRACED:
+ /*
+ * When we hit the race with PTRACE_ATTACH,
+ * we will not report this child. But the
+ * race means it has not yet been moved to
+ * our ptrace_children list, so we need to
+ * set the flag here to avoid a spurious ECHILD
+ * when the race happens with the only child.
+ */
+ flag = 1;
if (!my_ptrace_child(p))
continue;
/*FALLTHROUGH*/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
