memory leak in sctp_stream_init

memory leak in sctp_stream_init

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e31736d9 Merge tag 'nios2-v5.5-rc2' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=126a177ee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bbf3a35184a3ed64
dashboard link: https://syzkaller.appspot.com/bug?extid=772d9e36c490b18d51d1
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15602ddee00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12798251e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+772d9e36c490b18d51d1@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff8881080a3000 (size 4096):
   comm "syz-executor474", pid 7155, jiffies 4294942658 (age 15.870s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
   backtrace:
     [<00000000df094087>] genradix_alloc_node lib/generic-radix-tree.c:90  
[inline]
     [<00000000df094087>] __genradix_ptr_alloc+0xf5/0x250  
lib/generic-radix-tree.c:122
     [<0000000057cfa7bb>] __genradix_prealloc+0x46/0x70  
lib/generic-radix-tree.c:223
     [<0000000029d02dac>] sctp_stream_alloc_out.part.0+0x57/0x80  
net/sctp/stream.c:86
     [<00000000bb930a04>] sctp_stream_alloc_out net/sctp/stream.c:151  
[inline]
     [<00000000bb930a04>] sctp_stream_init+0x129/0x180 net/sctp/stream.c:129
     [<00000000ba13c246>] sctp_association_init net/sctp/associola.c:229  
[inline]
     [<00000000ba13c246>] sctp_association_new+0x46e/0x700  
net/sctp/associola.c:295
     [<000000008eb57b4d>] sctp_connect_new_asoc+0x90/0x220  
net/sctp/socket.c:1070
     [<00000000ea24e048>] __sctp_connect+0x182/0x3b0 net/sctp/socket.c:1176
     [<00000000aa2c530a>] __sctp_setsockopt_connectx+0xa9/0xf0  
net/sctp/socket.c:1322
     [<0000000018934bfd>] sctp_getsockopt_connectx3 net/sctp/socket.c:1407  
[inline]
     [<0000000018934bfd>] sctp_getsockopt net/sctp/socket.c:8079 [inline]
     [<0000000018934bfd>] sctp_getsockopt+0x1394/0x32f6  
net/sctp/socket.c:8010
     [<000000005fd7e3c8>] sock_common_getsockopt+0x38/0x50  
net/core/sock.c:3108
     [<00000000333baf72>] __sys_getsockopt+0xa8/0x180 net/socket.c:2162
     [<00000000de0f98e4>] __do_sys_getsockopt net/socket.c:2177 [inline]
     [<00000000de0f98e4>] __se_sys_getsockopt net/socket.c:2174 [inline]
     [<00000000de0f98e4>] __x64_sys_getsockopt+0x26/0x30 net/socket.c:2174
     [<00000000cf1dfee9>] do_syscall_64+0x73/0x220  
arch/x86/entry/common.c:294
     [<000000000f416860>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot can test patches for this bug, for details see:
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Re: memory leak in sctp_stream_init

[Neil Horman]

On Sun, Dec 15, 2019 at 12:35:09PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    e31736d9 Merge tag 'nios2-v5.5-rc2' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=126a177ee00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbf3a35184a3ed64
> dashboard link: https://syzkaller.appspot.com/bug?extid=772d9e36c490b18d51d1
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15602ddee00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12798251e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+772d9e36c490b18d51d1@syzkaller.appspotmail.com
> 
> BUG: memory leak
> unreferenced object 0xffff8881080a3000 (size 4096):
>   comm "syz-executor474", pid 7155, jiffies 4294942658 (age 15.870s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000df094087>] genradix_alloc_node lib/generic-radix-tree.c:90
> [inline]
>     [<00000000df094087>] __genradix_ptr_alloc+0xf5/0x250
> lib/generic-radix-tree.c:122
>     [<0000000057cfa7bb>] __genradix_prealloc+0x46/0x70
> lib/generic-radix-tree.c:223
>     [<0000000029d02dac>] sctp_stream_alloc_out.part.0+0x57/0x80
> net/sctp/stream.c:86
>     [<00000000bb930a04>] sctp_stream_alloc_out net/sctp/stream.c:151
> [inline]
>     [<00000000bb930a04>] sctp_stream_init+0x129/0x180 net/sctp/stream.c:129
>     [<00000000ba13c246>] sctp_association_init net/sctp/associola.c:229
> [inline]
>     [<00000000ba13c246>] sctp_association_new+0x46e/0x700
> net/sctp/associola.c:295
>     [<000000008eb57b4d>] sctp_connect_new_asoc+0x90/0x220
> net/sctp/socket.c:1070
>     [<00000000ea24e048>] __sctp_connect+0x182/0x3b0 net/sctp/socket.c:1176
>     [<00000000aa2c530a>] __sctp_setsockopt_connectx+0xa9/0xf0
> net/sctp/socket.c:1322
>     [<0000000018934bfd>] sctp_getsockopt_connectx3 net/sctp/socket.c:1407
> [inline]
>     [<0000000018934bfd>] sctp_getsockopt net/sctp/socket.c:8079 [inline]
>     [<0000000018934bfd>] sctp_getsockopt+0x1394/0x32f6
> net/sctp/socket.c:8010
>     [<000000005fd7e3c8>] sock_common_getsockopt+0x38/0x50
> net/core/sock.c:3108
>     [<00000000333baf72>] __sys_getsockopt+0xa8/0x180 net/socket.c:2162
>     [<00000000de0f98e4>] __do_sys_getsockopt net/socket.c:2177 [inline]
>     [<00000000de0f98e4>] __se_sys_getsockopt net/socket.c:2174 [inline]
>     [<00000000de0f98e4>] __x64_sys_getsockopt+0x26/0x30 net/socket.c:2174
>     [<00000000cf1dfee9>] do_syscall_64+0x73/0x220
> arch/x86/entry/common.c:294
>     [<000000000f416860>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 

Almost looks like we're processing a connectx socket option while the handling
of a cookie echo chunk is in flight through the state machine (i.e.
sctp_stream_update is getting called on the association while we're setting it
up in parallel), though I'm not sure how that can happen

Neil

> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 

Re: memory leak in sctp_stream_init

[Marcelo Ricardo Leitner]

On Mon, Dec 16, 2019 at 06:48:28AM -0500, Neil Horman wrote:
> On Sun, Dec 15, 2019 at 12:35:09PM -0800, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    e31736d9 Merge tag 'nios2-v5.5-rc2' of git://git.kernel.or..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=126a177ee00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=bbf3a35184a3ed64
> > dashboard link: https://syzkaller.appspot.com/bug?extid=772d9e36c490b18d51d1
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15602ddee00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12798251e00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+772d9e36c490b18d51d1@syzkaller.appspotmail.com
> > 
> > BUG: memory leak
> > unreferenced object 0xffff8881080a3000 (size 4096):
> >   comm "syz-executor474", pid 7155, jiffies 4294942658 (age 15.870s)
> >   hex dump (first 32 bytes):
> >     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >   backtrace:
> >     [<00000000df094087>] genradix_alloc_node lib/generic-radix-tree.c:90
> > [inline]
> >     [<00000000df094087>] __genradix_ptr_alloc+0xf5/0x250
> > lib/generic-radix-tree.c:122
> >     [<0000000057cfa7bb>] __genradix_prealloc+0x46/0x70
> > lib/generic-radix-tree.c:223
> >     [<0000000029d02dac>] sctp_stream_alloc_out.part.0+0x57/0x80
> > net/sctp/stream.c:86
> >     [<00000000bb930a04>] sctp_stream_alloc_out net/sctp/stream.c:151
> > [inline]
> >     [<00000000bb930a04>] sctp_stream_init+0x129/0x180 net/sctp/stream.c:129
> >     [<00000000ba13c246>] sctp_association_init net/sctp/associola.c:229
> > [inline]
> >     [<00000000ba13c246>] sctp_association_new+0x46e/0x700
> > net/sctp/associola.c:295
> >     [<000000008eb57b4d>] sctp_connect_new_asoc+0x90/0x220
> > net/sctp/socket.c:1070
> >     [<00000000ea24e048>] __sctp_connect+0x182/0x3b0 net/sctp/socket.c:1176
> >     [<00000000aa2c530a>] __sctp_setsockopt_connectx+0xa9/0xf0
> > net/sctp/socket.c:1322
> >     [<0000000018934bfd>] sctp_getsockopt_connectx3 net/sctp/socket.c:1407
> > [inline]
> >     [<0000000018934bfd>] sctp_getsockopt net/sctp/socket.c:8079 [inline]
> >     [<0000000018934bfd>] sctp_getsockopt+0x1394/0x32f6
> > net/sctp/socket.c:8010
> >     [<000000005fd7e3c8>] sock_common_getsockopt+0x38/0x50
> > net/core/sock.c:3108
> >     [<00000000333baf72>] __sys_getsockopt+0xa8/0x180 net/socket.c:2162
> >     [<00000000de0f98e4>] __do_sys_getsockopt net/socket.c:2177 [inline]
> >     [<00000000de0f98e4>] __se_sys_getsockopt net/socket.c:2174 [inline]
> >     [<00000000de0f98e4>] __x64_sys_getsockopt+0x26/0x30 net/socket.c:2174
> >     [<00000000cf1dfee9>] do_syscall_64+0x73/0x220
> > arch/x86/entry/common.c:294
> >     [<000000000f416860>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> 
> Almost looks like we're processing a connectx socket option while the handling
> of a cookie echo chunk is in flight through the state machine (i.e.
> sctp_stream_update is getting called on the association while we're setting it
> up in parallel), though I'm not sure how that can happen

I'm seeing something different. In the console output there were 2
fault injections and they hit the genradix preallocation. And our
handling of that error within genradix is the responsible for it:

sctp_stream_alloc_out()
{
...
        ret = genradix_prealloc(&stream->out, outcnt, gfp);
        if (ret)
                return ret;

        stream->outcnt = outcnt;
}

int __genradix_prealloc(struct __genradix *radix, size_t size,
                        gfp_t gfp_mask)
{
        size_t offset;

        for (offset = 0; offset < size; offset += PAGE_SIZE)
                if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
                        return -ENOMEM;

        return 0;
}

Note how it (and also __genradix_ptr_alloc()) doesn't clean up the
already, newly initialized, indexes.

Then it doesn't clean up the partially pre-allocated items on error
handling:

sctp_stream_init()
{
...
        ret = sctp_stream_alloc_out(stream, outcnt, gfp);
        if (ret)
                goto out;
...
        ret = sctp_stream_alloc_in(stream, incnt, gfp);
        if (ret) {
                sched->free(stream);
                genradix_free(&stream->out);   <--
                stream->outcnt = 0;
                goto out;
        }

out:
        return ret;
}

Considering that genradix_prealloc() failure is not fatal, seems the
fix here is to just ignore the failure in sctp_stream_alloc_out() and
let genradix try again later on.

  Marcelo

Re: memory leak in sctp_stream_init

[Marcelo Ricardo Leitner]

On Mon, Dec 16, 2019 at 11:56:38AM -0300, Marcelo Ricardo Leitner wrote:
...
> Considering that genradix_prealloc() failure is not fatal, seems the
> fix here is to just ignore the failure in sctp_stream_alloc_out() and
> let genradix try again later on.

Better yet, this fixes it here:

---8<---

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index df60b5ef24cb..e0b01bf912b3 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -84,8 +84,10 @@ static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
 		return 0;
 
 	ret = genradix_prealloc(&stream->out, outcnt, gfp);
-	if (ret)
+	if (ret) {
+		genradix_free(&stream->out);
 		return ret;
+	}
 
 	stream->outcnt = outcnt;
 	return 0;
@@ -100,8 +102,10 @@ static int sctp_stream_alloc_in(struct sctp_stream *stream, __u16 incnt,
 		return 0;
 
 	ret = genradix_prealloc(&stream->in, incnt, gfp);
-	if (ret)
+	if (ret) {
+		genradix_free(&stream->in);
 		return ret;
+	}
 
 	stream->incnt = incnt;
 	return 0;

Re: memory leak in sctp_stream_init

[Neil Horman]

On Mon, Dec 16, 2019 at 09:37:16PM -0300, Marcelo Ricardo Leitner wrote:
> On Mon, Dec 16, 2019 at 11:56:38AM -0300, Marcelo Ricardo Leitner wrote:
> ...
> > Considering that genradix_prealloc() failure is not fatal, seems the
> > fix here is to just ignore the failure in sctp_stream_alloc_out() and
> > let genradix try again later on.
> 
> Better yet, this fixes it here:
> 
> ---8<---
> 
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index df60b5ef24cb..e0b01bf912b3 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -84,8 +84,10 @@ static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
>  		return 0;
>  
>  	ret = genradix_prealloc(&stream->out, outcnt, gfp);
> -	if (ret)
> +	if (ret) {
> +		genradix_free(&stream->out);
>  		return ret;
> +	}
>  
>  	stream->outcnt = outcnt;
>  	return 0;
> @@ -100,8 +102,10 @@ static int sctp_stream_alloc_in(struct sctp_stream *stream, __u16 incnt,
>  		return 0;
>  
>  	ret = genradix_prealloc(&stream->in, incnt, gfp);
> -	if (ret)
> +	if (ret) {
> +		genradix_free(&stream->in);
>  		return ret;
> +	}
>  
>  	stream->incnt = incnt;
>  	return 0;
> 
I get how that fixes this, but that doesn't really seem like the right fix in my
mind.  Shouldn't genradix_prealloc internally free any memory its allocated if
it fails part way through its operation?

Neil