KASAN: slab-out-of-bounds Read in bpf_prog_create

KASAN: slab-out-of-bounds Read in bpf_prog_create

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    2015a28f Add linux-next specific files for 20190915
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11880d69600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=110691c2286b679a
dashboard link: https://syzkaller.appspot.com/bug?extid=eb853b51b10f1befa0b7
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=127c3481600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1150a70d600000

The bug was bisected to:

commit 2f4fa2db75e26995709043c8d3de4632ebed5c4b
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Thu Apr 18 03:48:01 2019 +0000

     compat_ioctl: unify copy-in of ppp filters

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=145eee1d600000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=165eee1d600000
console output: https://syzkaller.appspot.com/x/log.txt?x=125eee1d600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
Fixes: 2f4fa2db75e2 ("compat_ioctl: unify copy-in of ppp filters")

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:404 [inline]
BUG: KASAN: slab-out-of-bounds in bpf_prog_create+0xe9/0x250  
net/core/filter.c:1351
Read of size 32768 at addr ffff88809cf74000 by task syz-executor183/8575

CPU: 0 PID: 8575 Comm: syz-executor183 Not tainted 5.3.0-rc8-next-20190915  
#0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
  __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
  kasan_report+0x12/0x20 mm/kasan/common.c:634
  check_memory_region_inline mm/kasan/generic.c:185 [inline]
  check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
  memcpy+0x24/0x50 mm/kasan/common.c:122
  memcpy include/linux/string.h:404 [inline]
  bpf_prog_create+0xe9/0x250 net/core/filter.c:1351
  get_filter.isra.0+0x108/0x1a0 drivers/net/ppp/ppp_generic.c:572
  ppp_get_filter drivers/net/ppp/ppp_generic.c:584 [inline]
  ppp_ioctl+0x129d/0x2590 drivers/net/ppp/ppp_generic.c:801
  vfs_ioctl fs/ioctl.c:47 [inline]
  file_ioctl fs/ioctl.c:539 [inline]
  do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726
  ksys_ioctl+0xab/0xd0 fs/ioctl.c:743
  __do_sys_ioctl fs/ioctl.c:750 [inline]
  __se_sys_ioctl fs/ioctl.c:748 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748
  do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4401a9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffebb37d0a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401a9
RDX: 00000000200000c0 RSI: 0000000040107447 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a30
R13: 0000000000401ac0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8575:
  save_stack+0x23/0x90 mm/kasan/common.c:69
  set_track mm/kasan/common.c:77 [inline]
  __kasan_kmalloc mm/kasan/common.c:510 [inline]
  __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
  __do_kmalloc mm/slab.c:3655 [inline]
  __kmalloc_track_caller+0x15f/0x760 mm/slab.c:3670
  memdup_user+0x26/0xb0 mm/util.c:172
  get_filter.isra.0+0xd7/0x1a0 drivers/net/ppp/ppp_generic.c:568
  ppp_get_filter drivers/net/ppp/ppp_generic.c:584 [inline]
  ppp_ioctl+0x129d/0x2590 drivers/net/ppp/ppp_generic.c:801
  vfs_ioctl fs/ioctl.c:47 [inline]
  file_ioctl fs/ioctl.c:539 [inline]
  do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726
  ksys_ioctl+0xab/0xd0 fs/ioctl.c:743
  __do_sys_ioctl fs/ioctl.c:750 [inline]
  __se_sys_ioctl fs/ioctl.c:748 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748
  do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff88809cf74000
  which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 0 bytes inside of
  4096-byte region [ffff88809cf74000, ffff88809cf75000)
The buggy address belongs to the page:
page:ffffea000273dd00 refcount:1 mapcount:0 mapping:ffff8880aa402000  
index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002672988 ffffea00027e7788 ffff8880aa402000
raw: 0000000000000000 ffff88809cf74000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88809cf74f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff88809cf74f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff88809cf75000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                    ^
  ffff88809cf75080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88809cf75100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: KASAN: slab-out-of-bounds Read in bpf_prog_create

[Eric Biggers]

Arnd and Al,

On Tue, Sep 17, 2019 at 11:49:06AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    2015a28f Add linux-next specific files for 20190915
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=11880d69600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=110691c2286b679a
> dashboard link: https://syzkaller.appspot.com/bug?extid=eb853b51b10f1befa0b7
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=127c3481600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1150a70d600000
> 
> The bug was bisected to:
> 
> commit 2f4fa2db75e26995709043c8d3de4632ebed5c4b
> Author: Al Viro <viro@zeniv.linux.org.uk>
> Date:   Thu Apr 18 03:48:01 2019 +0000
> 
>     compat_ioctl: unify copy-in of ppp filters
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=145eee1d600000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=165eee1d600000
> console output: https://syzkaller.appspot.com/x/log.txt?x=125eee1d600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
> Fixes: 2f4fa2db75e2 ("compat_ioctl: unify copy-in of ppp filters")
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:404 [inline]
> BUG: KASAN: slab-out-of-bounds in bpf_prog_create+0xe9/0x250
> net/core/filter.c:1351
> Read of size 32768 at addr ffff88809cf74000 by task syz-executor183/8575
> 
> CPU: 0 PID: 8575 Comm: syz-executor183 Not tainted 5.3.0-rc8-next-20190915
> #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
>  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
>  __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
>  kasan_report+0x12/0x20 mm/kasan/common.c:634
>  check_memory_region_inline mm/kasan/generic.c:185 [inline]
>  check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
>  memcpy+0x24/0x50 mm/kasan/common.c:122
>  memcpy include/linux/string.h:404 [inline]
>  bpf_prog_create+0xe9/0x250 net/core/filter.c:1351
>  get_filter.isra.0+0x108/0x1a0 drivers/net/ppp/ppp_generic.c:572
>  ppp_get_filter drivers/net/ppp/ppp_generic.c:584 [inline]
>  ppp_ioctl+0x129d/0x2590 drivers/net/ppp/ppp_generic.c:801

This is a correct bisection.  This commit needs:

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 267fe2c58087..f55d7937d6c5 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -564,8 +564,9 @@ static struct bpf_prog *get_filter(struct sock_fprog *uprog)
 		return NULL;
 
 	/* uprog->len is unsigned short, so no overflow here */
-	fprog.len = uprog->len * sizeof(struct sock_filter);
-	fprog.filter = memdup_user(uprog->filter, fprog.len);
+	fprog.len = uprog->len;
+	fprog.filter = memdup_user(uprog->filter,
+				   uprog->len * sizeof(struct sock_filter));
 	if (IS_ERR(fprog.filter))
 		return ERR_CAST(fprog.filter);
 

Re: KASAN: slab-out-of-bounds Read in bpf_prog_create

[Eric Biggers]

Arnd and Al,

On Fri, Sep 27, 2019 at 08:15:10PM -0700, Eric Biggers wrote:
> Arnd and Al,
> 
> On Tue, Sep 17, 2019 at 11:49:06AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    2015a28f Add linux-next specific files for 20190915
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=11880d69600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=110691c2286b679a
> > dashboard link: https://syzkaller.appspot.com/bug?extid=eb853b51b10f1befa0b7
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=127c3481600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1150a70d600000
> > 
> > The bug was bisected to:
> > 
> > commit 2f4fa2db75e26995709043c8d3de4632ebed5c4b
> > Author: Al Viro <viro@zeniv.linux.org.uk>
> > Date:   Thu Apr 18 03:48:01 2019 +0000
> > 
> >     compat_ioctl: unify copy-in of ppp filters
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=145eee1d600000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=165eee1d600000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=125eee1d600000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
> > Fixes: 2f4fa2db75e2 ("compat_ioctl: unify copy-in of ppp filters")
> > 
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:404 [inline]
> > BUG: KASAN: slab-out-of-bounds in bpf_prog_create+0xe9/0x250
> > net/core/filter.c:1351
> > Read of size 32768 at addr ffff88809cf74000 by task syz-executor183/8575
> > 
> > CPU: 0 PID: 8575 Comm: syz-executor183 Not tainted 5.3.0-rc8-next-20190915
> > #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
> >  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
> >  __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
> >  kasan_report+0x12/0x20 mm/kasan/common.c:634
> >  check_memory_region_inline mm/kasan/generic.c:185 [inline]
> >  check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
> >  memcpy+0x24/0x50 mm/kasan/common.c:122
> >  memcpy include/linux/string.h:404 [inline]
> >  bpf_prog_create+0xe9/0x250 net/core/filter.c:1351
> >  get_filter.isra.0+0x108/0x1a0 drivers/net/ppp/ppp_generic.c:572
> >  ppp_get_filter drivers/net/ppp/ppp_generic.c:584 [inline]
> >  ppp_ioctl+0x129d/0x2590 drivers/net/ppp/ppp_generic.c:801
> 
> This is a correct bisection.  This commit needs:
> 
> diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
> index 267fe2c58087..f55d7937d6c5 100644
> --- a/drivers/net/ppp/ppp_generic.c
> +++ b/drivers/net/ppp/ppp_generic.c
> @@ -564,8 +564,9 @@ static struct bpf_prog *get_filter(struct sock_fprog *uprog)
>  		return NULL;
>  
>  	/* uprog->len is unsigned short, so no overflow here */
> -	fprog.len = uprog->len * sizeof(struct sock_filter);
> -	fprog.filter = memdup_user(uprog->filter, fprog.len);
> +	fprog.len = uprog->len;
> +	fprog.filter = memdup_user(uprog->filter,
> +				   uprog->len * sizeof(struct sock_filter));
>  	if (IS_ERR(fprog.filter))
>  		return ERR_CAST(fprog.filter);
>  

Why did you ignore this and merge the buggy commit to mainline anyway?
I even told you how to fix it...

- Eric

[PATCH] ppp: fix out-of-bounds access in bpf_prog_create()

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

sock_fprog_kern::len is in units of struct sock_filter, not bytes.

Fixes: 3e859adf3643 ("compat_ioctl: unify copy-in of ppp filters")
Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/net/ppp/ppp_generic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 0cb1c2d0a8bc..3bf8a8b42983 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -564,8 +564,9 @@ static struct bpf_prog *get_filter(struct sock_fprog *uprog)
 		return NULL;
 
 	/* uprog->len is unsigned short, so no overflow here */
-	fprog.len = uprog->len * sizeof(struct sock_filter);
-	fprog.filter = memdup_user(uprog->filter, fprog.len);
+	fprog.len = uprog->len;
+	fprog.filter = memdup_user(uprog->filter,
+				   uprog->len * sizeof(struct sock_filter));
 	if (IS_ERR(fprog.filter))
 		return ERR_CAST(fprog.filter);
 
-- 
2.24.0

Re: [PATCH] ppp: fix out-of-bounds access in bpf_prog_create()

[Arnd Bergmann]

On Thu, Dec 5, 2019 at 6:55 AM Eric Biggers <ebiggers@kernel.org> wrote:
>
> From: Eric Biggers <ebiggers@google.com>
>
> sock_fprog_kern::len is in units of struct sock_filter, not bytes.
>
> Fixes: 3e859adf3643 ("compat_ioctl: unify copy-in of ppp filters")
> Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

Thanks for fixing the bug I introduced!

Re: KASAN: slab-out-of-bounds Read in bpf_prog_create

[Arnd Bergmann]

On Thu, Dec 5, 2019 at 6:22 AM Eric Biggers <ebiggers@kernel.org> wrote:

> >
>
> Why did you ignore this and merge the buggy commit to mainline anyway?
> I even told you how to fix it...

I'm sorry about this, I completely missed the email about it originally.

      Arnd

Re: [PATCH] ppp: fix out-of-bounds access in bpf_prog_create()

[David Miller]

From: Eric Biggers <ebiggers@kernel.org>
Date: Wed,  4 Dec 2019 21:54:19 -0800

> From: Eric Biggers <ebiggers@google.com>
> 
> sock_fprog_kern::len is in units of struct sock_filter, not bytes.
> 
> Fixes: 3e859adf3643 ("compat_ioctl: unify copy-in of ppp filters")
> Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Applied, thank you.