[PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[kan.liang]

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>
---
 tools/perf/util/mmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 38ca3ff..f6cfc52 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -317,5 +317,11 @@ int perf_mmap__push(struct perf_mmap *md, void *to,
  */
 void perf_mmap__read_done(struct perf_mmap *map)
 {
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!refcount_read(&map->refcnt))
+		return;
+
 	map->prev = perf_mmap__read_head(map);
 }
-- 
2.4.11

Re: [PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[Arnaldo Carvalho de Melo]

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 ~]#

- Arnaldo

Re: [PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[Arnaldo Carvalho de Melo]

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.

- 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))
 {

Re: [PATCH] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[Liang, Kan]

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))
>   {
> 

[tip:perf/core] perf mmap: Be consistent when checking for an unmaped ring buffer

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  895e3b06fc2ce438adc62cb13d31ea001dcfda16
Gitweb:     https://git.kernel.org/tip/895e3b06fc2ce438adc62cb13d31ea001dcfda16
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Mon, 26 Mar 2018 11:42:15 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 27 Mar 2018 13:13:38 -0300

perf mmap: Be consistent when checking for an unmaped ring buffer

The previous patch is insufficient to cure the reported 'perf trace'
segfault, as it only cures the perf_mmap__read_done() case, moving the
segfault to perf_mmap__read_init() functio, fix it by doing the same
refcount check.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 8872481bd048 ("perf mmap: Introduce perf_mmap__read_init()")
Link: https://lkml.kernel.org/r/20180326144127.GF18897@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/mmap.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

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))
 {

[tip:perf/core] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

[tip-bot for Kan Liang]

Commit-ID:  f58385f629c87a9e210108b39c1f4950d0363ad2
Gitweb:     https://git.kernel.org/tip/f58385f629c87a9e210108b39c1f4950d0363ad2
Author:     Kan Liang <kan.liang@linux.intel.com>
AuthorDate: Mon, 26 Mar 2018 09:42:09 -0400
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 27 Mar 2018 13:13:38 -0300

perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done()

There is a 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().

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: ee023de05f35 ("perf mmap: Introduce perf_mmap__read_done()")
Link: http://lkml.kernel.org/r/1522071729-16776-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/mmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 38ca3ffb9d61..f6cfc52ff1fe 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -317,5 +317,11 @@ out:
  */
 void perf_mmap__read_done(struct perf_mmap *map)
 {
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!refcount_read(&map->refcnt))
+		return;
+
 	map->prev = perf_mmap__read_head(map);
 }