Messages in this thread | | | Subject | Re: [PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done() | From | "Liang, Kan" <> | Date | Mon, 26 Mar 2018 10:51:37 -0400 |
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On 3/26/2018 10:41 AM, Arnaldo Carvalho de Melo wrote: > Em Mon, Mar 26, 2018 at 11:26:04AM -0300, Arnaldo Carvalho de Melo escreveu: >> Em Mon, Mar 26, 2018 at 09:42:09AM -0400, kan.liang@linux.intel.com escreveu: >>> From: Kan Liang <kan.liang@linux.intel.com> >>> >>> There is segmentation fault when running perf trace. For example, >>> [root@jouet e]# perf trace -e *chdir -o /tmp/bla perf report >>> --ignore-vmlinux -i ../perf.data >>> >>> The perf_mmap__consume() could unmap the mmap. It needs to check the >>> refcnt in perf_mmap__read_done(). >>> >>> Fixes: ee023de05f35 ("perf mmap: Introduce perf_mmap__read_done()") >>> Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com> >>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> >> >> Seems insuficient: >> >> [root@jouet ~]# perf trace -e *chdir -o /tmp/bla perf report --ignore-vmlinux >> perf: Segmentation fault >> Obtained 9 stack frames. >> perf(sighandler_dump_stack+0x3e) [0x4fe31e] >> /lib64/libc.so.6(+0x346df) [0x7fc0c3ced6df] >> perf(perf_mmap__read_init+0x26) [0x4ccd06] >> perf(cmd_trace+0x1bf6) [0x47bb76] >> perf() [0x4a824e] >> perf() [0x4a8550] >> perf(main+0x331) [0x42bef1] >> /lib64/libc.so.6(__libc_start_main+0xe9) [0x7fc0c3cd9f29] >> perf(_start+0x29) [0x42c319] >> Segmentation fault (core dumped) >> [root@jouet ~]# > > I'm adding this as a separate patch, with yours and this one, the > segfault is gone. >
Thanks. Yes, we should check the mmap before using it for all new interfaces.
Thanks, Kan
> - Arnaldo > > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c > index f6cfc52ff1fe..fc832676a798 100644 > --- a/tools/perf/util/mmap.c > +++ b/tools/perf/util/mmap.c > @@ -234,7 +234,7 @@ static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end) > /* > * Report the start and end of the available data in ringbuffer > */ > -int perf_mmap__read_init(struct perf_mmap *md) > +static int __perf_mmap__read_init(struct perf_mmap *md) > { > u64 head = perf_mmap__read_head(md); > u64 old = md->prev; > @@ -268,6 +268,17 @@ int perf_mmap__read_init(struct perf_mmap *md) > return 0; > } > > +int perf_mmap__read_init(struct perf_mmap *map) > +{ > + /* > + * Check if event was unmapped due to a POLLHUP/POLLERR. > + */ > + if (!refcount_read(&map->refcnt)) > + return -ENOENT; > + > + return __perf_mmap__read_init(map); > +} > + > int perf_mmap__push(struct perf_mmap *md, void *to, > int push(void *to, void *buf, size_t size)) > { >
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