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New: BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

Bug 206525 [email protected] 3 participants 11 messages Feb 13, 2020 – Feb 26, 2020

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#0 lore raw

https://bugzilla.kernel.org/show_bug.cgi?id=206525

            Bug ID: 206525
           Summary: BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44
                    (kernel 5.6-rc1)
           Product: Platform Specific/Hardware
           Version: 2.5
    Kernel Version: 5.6.0-rc1
          Hardware: PPC-32
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: PPC-32
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

Created attachment 287357
--> https://bugzilla.kernel.org/attachment.cgi?id=287357&action=edit
dmesg (5.6.0-rc1 + v2 Fix DSI and ISI... patch, PowerMac G4 DP)

[...]

Feb 13 20:18:53 T600 kernel:
==================================================================
Feb 13 20:18:53 T600 kernel: BUG: KASAN: stack-out-of-bounds in
test_bit+0x30/0x44
Feb 13 20:18:53 T600 kernel: Read of size 4 at addr ee8bddac by task systemd/1
Feb 13 20:18:53 T600 kernel: 
Feb 13 20:18:53 T600 kernel: CPU: 0 PID: 1 Comm: systemd Tainted: G        W   
     5.6.0-rc1-PowerMacG4+ #20
Feb 13 20:18:53 T600 kernel: Call Trace:
Feb 13 20:18:53 T600 kernel: [ee8bdc38] [c078cf18] dump_stack+0xbc/0x118
(unreliable)
Feb 13 20:18:53 T600 kernel: [ee8bdc68] [c0249f94]
print_address_description.isra.0+0x3c/0x420
Feb 13 20:18:53 T600 kernel: [ee8bdcf8] [c024a554] __kasan_report+0x138/0x180
Feb 13 20:18:53 T600 kernel: [ee8bdd38] [c0249718] kasan_report+0x7c/0x104
Feb 13 20:18:53 T600 kernel: [ee8bdd58] [c06526b4] test_bit+0x30/0x44
Feb 13 20:18:53 T600 kernel: [ee8bdd78] [c0657c6c] netlink_bind+0x24c/0x33c
Feb 13 20:18:53 T600 kernel: [ee8bde18] [c05c0c3c] __sys_bind+0xd4/0x120
Feb 13 20:18:53 T600 kernel: [ee8bdf38] [c001a278] ret_from_syscall+0x0/0x34
Feb 13 20:18:53 T600 kernel: --- interrupt: c01 at 0x4f3ea8
                                 LR = 0x8f5b80
Feb 13 20:18:53 T600 kernel: 
Feb 13 20:18:53 T600 kernel: The buggy address belongs to the page:
Feb 13 20:18:53 T600 kernel: page:ef460a94 refcount:0 mapcount:0
mapping:00000000 index:0x0
Feb 13 20:18:53 T600 kernel: flags: 0x0()
Feb 13 20:18:53 T600 kernel: raw: 00000000 ef460a98 ef460a98 00000000 00000000
00000000 ffffffff 00000000
Feb 13 20:18:53 T600 kernel: raw: 00000000
Feb 13 20:18:53 T600 kernel: page dumped because: kasan: bad access detected
Feb 13 20:18:53 T600 kernel: 
Feb 13 20:18:53 T600 kernel: addr ee8bddac is located in stack of task
systemd/1 at offset 36 in frame:
Feb 13 20:18:53 T600 kernel:  netlink_bind+0x0/0x33c
Feb 13 20:18:53 T600 kernel: 
Feb 13 20:18:53 T600 kernel: this frame has 1 object:
Feb 13 20:18:53 T600 kernel:  [32, 36) 'groups'
Feb 13 20:18:53 T600 kernel: 
Feb 13 20:18:53 T600 kernel: Memory state around the buggy address:
Feb 13 20:18:53 T600 kernel:  ee8bdc80: 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00
Feb 13 20:18:53 T600 kernel:  ee8bdd00: 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00
Feb 13 20:18:53 T600 kernel: >ee8bdd80: 00 f1 f1 f1 f1 04 f3 f3 f3 00 00 00 00
00 00 00
Feb 13 20:18:53 T600 kernel:                           ^
Feb 13 20:18:53 T600 kernel:  ee8bde00: 00 00 00 00 00 f1 f1 f1 f1 04 f2 04 f2
00 00 00
Feb 13 20:18:53 T600 kernel:  ee8bde80: 00 00 00 00 00 00 00 00 00 00 00 00 00
f3 f3 f3
Feb 13 20:18:53 T600 kernel:

==================================================================

Happens on my G4 DP with kernel 5.6.0-rc1 and KASAN enabled (outline) during boot. kernel is patched with Christophe's '[v2] powerpc/32s: Fix DSI and ISI exceptions for CONFIG_VMAP_STACK' (https://patchwork.ozlabs.org/patch/1237387/)
but CONFIG_VMAP_STACK was not used here.

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#2 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

Christophe Leroy ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #2 from Christophe Leroy ([email protected]) --- Probably a bug in or around netlink_bind() in net/netlink/af_netlink.c
https://elixir.bootlin.com/linux/v5.6-rc1/source/net/netlink/af_netlink.c#L1017

Could you print the value of nlk->ngroups just before the loop which does the test_bit() ? It shall be 32 or less.

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#3 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

--- Comment #3 from Christophe Leroy ([email protected]) --- Bug introduced by commit ("cf5bddb95cbe net: bridge: vlan: add rtnetlink group and notify support")

RTNLGRP_MAX is now 33.

'unsigned long groups' is 32 bits long on PPC32

Following loop in netlink_bind() overflows.

                for (group = 0; group < nlk->ngroups; group++) {
                        if (!test_bit(group, &groups))
                                continue;
                        err = nlk->netlink_bind(net, group + 1);
                        if (!err)
                                continue;
                        netlink_undo_bind(group, groups, sk);
                        goto unlock;
                }

Should 'groups' be changes to 'unsigned long long' ?

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#4 lore raw

[netlink_bind()] [Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

-------- Message transféré --------
Sujet : [Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1) Date : Sat, 15 Feb 2020 17:52:44 +0000
De : [email protected]
Pour : [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

--- Comment #3 from Christophe Leroy ([email protected]) --- Bug introduced by commit ("cf5bddb95cbe net: bridge: vlan: add rtnetlink group and notify support")

RTNLGRP_MAX is now 33.

'unsigned long groups' is 32 bits long on PPC32

Following loop in netlink_bind() overflows.

                for (group = 0; group < nlk->ngroups; group++) {
                        if (!test_bit(group, &groups))
                                continue;
                        err = nlk->netlink_bind(net, group + 1);
                        if (!err)
                                continue;
                        netlink_undo_bind(group, groups, sk);
                        goto unlock;
                }

Should 'groups' be changes to 'unsigned long long' ?

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#5 lore raw

Re: [netlink_bind()] [Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

Quoted 33 lines · Christophe Leroy

-------- Message transféré --------
Sujet : [Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1) Date : Sat, 15 Feb 2020 17:52:44 +0000
De : [email protected]
Pour : [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

--- Comment #3 from Christophe Leroy ([email protected]) --- Bug introduced by commit ("cf5bddb95cbe net: bridge: vlan: add rtnetlink group and notify support")

RTNLGRP_MAX is now 33.

'unsigned long groups' is 32 bits long on PPC32

Following loop in netlink_bind() overflows.

                for (group = 0; group < nlk->ngroups; group++) { if (!test_bit(group, &groups)) continue;
                        err = nlk->netlink_bind(net, group + 1); if (!err)
                                continue; netlink_undo_bind(group, groups, sk); goto unlock;
                }

Quoted 2 lines

Should 'groups' be changes to 'unsigned long long' ?

Hi,
I'm currently traveling and will be able to look into this properly in a few days, but I think we can just cap these at min(BITS_PER_TYPE(u32), nlk->ngroups) since "groups" is coming from sockaddr_nl's "nl_groups" which is a u32, for any groups beyond u32 one has to use setsockopt().

Cheers,
Nik

author
#6 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

--- Comment #4 from Christophe Leroy ([email protected]) --- Feedback from Nikolay:

I think we can just cap these at min(BITS_PER_TYPE(u32), nlk->ngroups) since "groups" is coming from sockaddr_nl's "nl_groups" which is a u32, for any groups beyond u32 one has to use setsockopt().

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#8 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

Erhard F. ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

          Component|PPC-32                      |Other
           Hardware|PPC-32                      |All
            Product|Platform Specific/Hardware  |Networking
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#9 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

--- Comment #6 from Nikolay Aleksandrov ([email protected]) --- Note that the bug wasn't introduced by my commit, but instead has been there since:
commit 4f520900522f
Author: Richard Guy Briggs <[email protected]>
Date: Tue Apr 22 21:31:54 2014 -0400

netlink: have netlink per-protocol bind function return an error code.

which moved the ngroups test_bit() to a local variable. My commit only exposed the bug since it added the 33rd group. I'm currently preparing a fix and will post it to netdev after verifying and testing it.

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#10 lore raw

[Bug 206525] BUG: KASAN: stack-out-of-bounds in test_bit+0x30/0x44 (kernel 5.6-rc1)

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=206525

Erhard F. ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
         Resolution|---                         |CODE_FIX

--- Comment #7 from Erhard F. ([email protected]) --- Fix landed in 5.6-rc3, works now as expected. Thanks!

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