LinuxLists.cc - [patch] perf tool divide by zero error if f_header.attr

2019-07-24 00:22:40

Subject: [patch] perf tool divide by zero error if f_header.attr_size==0

Hello

so I have been having lots of trouble with hand-crafted perf.data files
causing segfaults and the like, so I have started fuzzing the perf tool.

First issue found:

If f_header.attr_size is 0 in the perf.data file, then perf will crash
with a divide-by-zero error.

Signed-off-by: Vince Weaver <[email protected]>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c24db7f4909c..26df60ee9460 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3559,6 +3559,10 @@ int perf_session__read_header(struct perf_session *session)
data->file.path);
}

+ if (f_header.attr_size == 0) {
+ return -EINVAL;
+ }
+
nr_attrs = f_header.attrs.size / f_header.attr_size;
lseek(fd, f_header.attrs.offset, SEEK_SET);

2019-07-24 00:33:19

by Arnaldo Carvalho de Melo

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Subject: Re: [patch] perf tool divide by zero error if f_header.attr_size==0

2019-07-24 02:30:52

by Vince Weaver

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Subject: [patch] perf tool buffer overflow in perf_header__read_build_ids

Hello

my perf_tool_fuzzer has found another issue, this one a buffer overflow
in perf_header__read_build_ids. The build id filename is read in with a
filename length read from the perf.data file, but this can be longer than
PATH_MAX which will smash the stack.

This might not be the right fix, not sure if filename should be NUL
terminated or not.

Signed-off-by: Vince Weaver <[email protected]>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c24db7f4909c..9a893a26e678 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
perf_event_header__bswap(&bev.header);

len = bev.header.size - sizeof(bev);
+
+ if (len>PATH_MAX) len=PATH_MAX;
+
if (readn(input, filename, len) != len)
goto out;
/*

2019-07-26 19:52:14

by Arnaldo Carvalho de Melo

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Subject: Re: [patch] perf tool divide by zero error if f_header.attr_size==0

Em Tue, Jul 23, 2019 at 11:06:01AM -0400, Vince Weaver escreveu:
> Hello
>
> so I have been having lots of trouble with hand-crafted perf.data files
> causing segfaults and the like, so I have started fuzzing the perf tool.
>
> First issue found:
>
> If f_header.attr_size is 0 in the perf.data file, then perf will crash
> with a divide-by-zero error.
>
> Signed-off-by: Vince Weaver <[email protected]>

I added this on top:

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 25f89d0790fe..47877f0f6667 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3560,6 +3560,9 @@ int perf_session__read_header(struct perf_session *session)
}

if (f_header.attr_size == 0) {
+ pr_err("ERROR: The %s file's attr size field is 0 which is unexpected.\n"
+ "Was the 'perf record' command properly terminated?\n",
+ data->file.path);
return -EINVAL;
}

[acme@quaco perf]$

Thanks, applied.

- Arnaldo

>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..26df60ee9460 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -3559,6 +3559,10 @@ int perf_session__read_header(struct perf_session *session)
> data->file.path);
> }
>
> + if (f_header.attr_size == 0) {
> + return -EINVAL;
> + }
> +
> nr_attrs = f_header.attrs.size / f_header.attr_size;
> lseek(fd, f_header.attrs.offset, SEEK_SET);
>

--

- Arnaldo

2019-07-26 19:54:29

by Arnaldo Carvalho de Melo

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Subject: Re: [patch] perf tool buffer overflow in perf_header__read_build_ids

Em Tue, Jul 23, 2019 at 04:42:30PM -0400, Vince Weaver escreveu:
> Hello
>
> my perf_tool_fuzzer has found another issue, this one a buffer overflow
> in perf_header__read_build_ids. The build id filename is read in with a
> filename length read from the perf.data file, but this can be longer than
> PATH_MAX which will smash the stack.
>
> This might not be the right fix, not sure if filename should be NUL
> terminated or not.
>
> Signed-off-by: Vince Weaver <[email protected]>
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..9a893a26e678 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
> perf_event_header__bswap(&bev.header);
>
> len = bev.header.size - sizeof(bev);
> +
> + if (len>PATH_MAX) len=PATH_MAX;
> +

Humm, I wonder if we shouldn't just declare the whole file invalid like
you did with the previous patch?

- Arnaldo

> if (readn(input, filename, len) != len)
> goto out;
> /*

2019-07-29 21:37:21

by tip-bot for Vasyl Gomonovych

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Subject: [tip:perf/urgent] perf header: Fix divide by zero error if f_header.attr_size==0

Commit-ID: 7622236ceb167aa3857395f9bdaf871442aa467e
Gitweb: https://git.kernel.org/tip/7622236ceb167aa3857395f9bdaf871442aa467e
Author: Vince Weaver <[email protected]>
AuthorDate: Tue, 23 Jul 2019 11:06:01 -0400
Committer: Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 29 Jul 2019 09:03:43 -0300

perf header: Fix divide by zero error if f_header.attr_size==0

So I have been having lots of trouble with hand-crafted perf.data files
causing segfaults and the like, so I have started fuzzing the perf tool.

First issue found:

If f_header.attr_size is 0 in the perf.data file, then perf will crash
with a divide-by-zero error.

Committer note:

Added a pr_err() to tell the user why the command failed.

Signed-off-by: Vince Weaver <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1907231100440.14532@macbook-air
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/util/header.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 20111f8da5cb..47877f0f6667 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3559,6 +3559,13 @@ int perf_session__read_header(struct perf_session *session)
data->file.path);
}

+ if (f_header.attr_size == 0) {
+ pr_err("ERROR: The %s file's attr size field is 0 which is unexpected.\n"
+ "Was the 'perf record' command properly terminated?\n",
+ data->file.path);
+ return -EINVAL;
+ }
+
nr_attrs = f_header.attrs.size / f_header.attr_size;
lseek(fd, f_header.attrs.offset, SEEK_SET);

2019-08-23 23:39:19

by Vince Weaver

[permalink] [raw]

Subject: Re: [patch] perf tool buffer overflow in perf_header__read_build_ids

On Fri, 26 Jul 2019, Arnaldo Carvalho de Melo wrote:

> Em Tue, Jul 23, 2019 at 04:42:30PM -0400, Vince Weaver escreveu:
> > my perf_tool_fuzzer has found another issue, this one a buffer overflow
> > in perf_header__read_build_ids. The build id filename is read in with a
> > filename length read from the perf.data file, but this can be longer than
> > PATH_MAX which will smash the stack.
> >
> > This might not be the right fix, not sure if filename should be NUL
> > terminated or not.
> >
> > Signed-off-by: Vince Weaver <[email protected]>
> >
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index c24db7f4909c..9a893a26e678 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
> > perf_event_header__bswap(&bev.header);
> >
> > len = bev.header.size - sizeof(bev);
> > +
> > + if (len>PATH_MAX) len=PATH_MAX;
> > +
>
> Humm, I wonder if we shouldn't just declare the whole file invalid like
> you did with the previous patch?
>
> - Arnaldo
>
> > if (readn(input, filename, len) != len)
> > goto out;
> > /*

did we ever decide how to fix this issue? Or were you waiting on a
followup patch from me?

This is actually an exploitable security bug if you can convince someone
to run "perf" on an untrusted perf.data file.

Vince

2019-08-25 14:34:15

by Arnaldo Carvalho de Melo

[permalink] [raw]

Subject: Re: [patch] perf tool buffer overflow in perf_header__read_build_ids

Em Fri, Aug 23, 2019 at 04:42:47PM -0400, Vince Weaver escreveu:
> On Fri, 26 Jul 2019, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Jul 23, 2019 at 04:42:30PM -0400, Vince Weaver escreveu:
> > > my perf_tool_fuzzer has found another issue, this one a buffer overflow
> > > in perf_header__read_build_ids. The build id filename is read in with a
> > > filename length read from the perf.data file, but this can be longer than
> > > PATH_MAX which will smash the stack.
> > >
> > > This might not be the right fix, not sure if filename should be NUL
> > > terminated or not.
> > >
> > > Signed-off-by: Vince Weaver <[email protected]>
> > >
> > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > > index c24db7f4909c..9a893a26e678 100644
> > > --- a/tools/perf/util/header.c
> > > +++ b/tools/perf/util/header.c
> > > @@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
> > > perf_event_header__bswap(&bev.header);
> > >
> > > len = bev.header.size - sizeof(bev);
> > > +
> > > + if (len>PATH_MAX) len=PATH_MAX;
> > > +
> >
> > Humm, I wonder if we shouldn't just declare the whole file invalid like
> > you did with the previous patch?

> > > if (readn(input, filename, len) != len)
> > > goto out;
> > > /*
>
> did we ever decide how to fix this issue? Or were you waiting on a
> followup patch from me?

Fell thru the cracks, but yeah, I was waiting for a patch, can you send
it?

- Arnaldo

> This is actually an exploitable security bug if you can convince someone
> to run "perf" on an untrusted perf.data file.

Indeed, and in light of the current discussion about unprivileged eBPF I
think we should start dropping privileges in perf report, etc.

- Arnaldo