Messages in this thread Patch in this message | | | From | Dmitry Vyukov <> | Date | Sat, 20 Jan 2018 16:06:57 +0100 | Subject | Re: Possible Memory Leak in KCOV Linux 4.15-rc1 |
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On Sat, Jan 20, 2018 at 4:01 PM, Shankara Pailoor <sp3485@columbia.edu> wrote: > Hi Dmitry, > > I will try and get something to you tomorrow. Just wondering, but what > happens to the old struct kcov if a task opens /sys/kernel/debug/kcov > twice? I am looking here > https://elixir.free-electrons.com/linux/v4.15-rc8/source/kernel/kcov.c#L381 > and I don't see where the previous struct would get freed.
Good question. Perhaps we need something like:
diff --git a/kernel/kcov.c b/kernel/kcov.c index 7594c033d98a..c76498018500 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -358,7 +358,7 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, */ if (kcov->mode != KCOV_MODE_INIT || !kcov->area) return -EINVAL; - if (kcov->t != NULL) + if (kcov->t != NULL || t->kcov != NULL) return -EBUSY; if (arg == KCOV_TRACE_PC) kcov->mode = KCOV_MODE_TRACE_PC;
> On Sat, Jan 20, 2018 at 4:38 AM, Dmitry Vyukov <dvyukov@google.com> wrote: >> On Fri, Jan 19, 2018 at 8:29 PM, Shankara Pailoor <sp3485@columbia.edu> wrote: >>> Hi Dmitry, >>> >>> I added support for kcov in strace and I have been tracing a fairly >>> large program but after a little while, I notice that when I mmap a >>> new cover buffer, the call fails with ENOMEM. After killing the >>> program, I try and rerun and I notice that there is nearly no memory >>> on the system. When I do a kmemleak scan I get the following reports: >>> >>> I believe the problem occurs when I try and setup the kcov buffer >>> again after an exec. Instead of reusing the old file descriptor I open >>> kcov again within that process. In that case, I don't know what >>> happens to the old kcov struct. >>> >>> I don't see a maintainers list for kcov so I decided to email you >>> directly. Let me know what more information I can provide. >> >> >> Hi Shankara, >> >> Looks bad. Can you provide a reproducer? >> We extensively use kcov with syzkaller, but have not observed such >> leaks. Also I don't see anything obvious in the code. >> >> Thanks >
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