[syzbot] [net?] KASAN: slab-out-of-bounds Read in dns_resolver_preparse

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 48e8992e33ab Add linux-next specific files for 20231213
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=155c1ac1e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=978b8aaa2e92a8f
dashboard link: https://syzkaller.appspot.com/bug?extid=94bbb75204a05da3d89f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e0a966e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1555a15ce80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ade5327f8151/disk-48e8992e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/16bff810e759/vmlinux-48e8992e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/14c4448589de/bzImage-48e8992e.xz

The issue was bisected to:

commit b946001d3bb1202e90093cf5e72dbcb20e2689a0
Author: David Howells <dhow...@redhat.com>
Date: Sat Dec 9 00:41:55 2023 +0000

keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10c349c1e80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12c349c1e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=14c349c1e80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+94bbb7...@syzkaller.appspotmail.com
Fixes: b946001d3bb1 ("keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry")

==================================================================
BUG: KASAN: slab-out-of-bounds in dns_resolver_preparse+0xc9f/0xd60 net/dns_resolver/dns_key.c:127
Read of size 1 at addr ffff888028894084 by task syz-executor265/5069

CPU: 0 PID: 5069 Comm: syz-executor265 Not tainted 6.7.0-rc5-next-20231213-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:377 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:488
kasan_report+0xd9/0x110 mm/kasan/report.c:601
dns_resolver_preparse+0xc9f/0xd60 net/dns_resolver/dns_key.c:127
__key_create_or_update+0x453/0xdf0 security/keys/key.c:842
key_create_or_update+0x42/0x50 security/keys/key.c:1007
__do_sys_add_key+0x29c/0x450 security/keys/keyctl.c:134
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x62/0x6a
RIP: 0033:0x7fd37f34f2e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff2f4f3198 EFLAGS: 00000246 ORIG_RAX: 00000000000000f8
RAX: ffffffffffffffda RBX: 00007fff2f4f3368 RCX: 00007fd37f34f2e9
RDX: 0000000020000080 RSI: 0000000000000000 RDI: 00000000200003c0
RBP: 00007fd37f3c2610 R08: 0000000002853c32 R09: 00007fff2f4f3368
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff2f4f3358 R14: 0000000000000001 R15: 0000000000000001
</TASK>

Allocated by task 5069:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:47
kasan_set_track+0x24/0x30 mm/kasan/common.c:61
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slub.c:3985 [inline]
__kmalloc_node+0x226/0x480 mm/slub.c:3992
kmalloc_node include/linux/slab.h:610 [inline]
kvmalloc_node+0x99/0x1a0 mm/util.c:617
kvmalloc include/linux/slab.h:728 [inline]
__do_sys_add_key+0x1f8/0x450 security/keys/keyctl.c:116
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x62/0x6a

The buggy address belongs to the object at ffff888028894080
which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of
allocated 4-byte region [ffff888028894080, ffff888028894084)

The buggy address belongs to the physical page:
page:ffffea0000a22500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x28894
anon flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888013041280 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080800080 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (swapper/0), ts 27978623390, free_ts 27978121808
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2d0/0x350 mm/page_alloc.c:1540
prep_new_page mm/page_alloc.c:1547 [inline]
get_page_from_freelist+0xa19/0x3740 mm/page_alloc.c:3355
__alloc_pages+0x22e/0x2410 mm/page_alloc.c:4611
alloc_pages_mpol+0x258/0x5f0 mm/mempolicy.c:2133
alloc_slab_page mm/slub.c:2191 [inline]
allocate_slab mm/slub.c:2358 [inline]
new_slab+0x283/0x3c0 mm/slub.c:2411
___slab_alloc+0x4ab/0x1990 mm/slub.c:3544
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3629
__slab_alloc_node mm/slub.c:3682 [inline]
slab_alloc_node mm/slub.c:3854 [inline]
__do_kmalloc_node mm/slub.c:3984 [inline]
__kmalloc_node_track_caller+0x367/0x470 mm/slub.c:4005
kstrdup+0x3c/0x70 mm/util.c:62
kstrdup_const+0x5f/0x70 mm/util.c:85
kvasprintf_const+0x10b/0x190 lib/kasprintf.c:48
kobject_set_name_vargs+0x5a/0x130 lib/kobject.c:272
kobject_add_varg lib/kobject.c:366 [inline]
kobject_init_and_add+0xe8/0x190 lib/kobject.c:455
locate_module_kobject+0xef/0x190 kernel/params.c:781
kernel_add_sysfs_param kernel/params.c:808 [inline]
param_sysfs_builtin kernel/params.c:856 [inline]
param_sysfs_builtin_init+0x25f/0x450 kernel/params.c:990
do_one_initcall+0x128/0x680 init/main.c:1236
page last free pid 3062 tgid 3062 stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1140 [inline]
free_unref_page_prepare+0x51f/0xb10 mm/page_alloc.c:2390
free_unref_page+0x33/0x3b0 mm/page_alloc.c:2530
mm_free_pgd kernel/fork.c:799 [inline]
__mmdrop+0xd5/0x470 kernel/fork.c:915
mmdrop include/linux/sched/mm.h:54 [inline]
__mmput+0x40a/0x4d0 kernel/fork.c:1352
mmput+0x62/0x70 kernel/fork.c:1363
free_bprm+0x143/0x3e0 fs/exec.c:1490
kernel_execve+0x3e6/0x4e0 fs/exec.c:2036
call_usermodehelper_exec_async+0x252/0x4c0 kernel/umh.c:110
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Memory state around the buggy address:
ffff888028893f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888028894000: 07 fc fc fc 07 fc fc fc fa fc fc fc 05 fc fc fc
>ffff888028894080: 04 fc fc fc fb fc fc fc fb fc fc fc 06 fc fc fc
^
ffff888028894100: 06 fc fc fc fb fc fc fc 00 fc fc fc 00 fc fc fc
ffff888028894180: fb fc fc fc 04 fc fc fc 04 fc fc fc fb fc fc fc
==================================================================


---
This report 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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Edward Adam Davis]

please test slab-out-of-bounds Read in dns_resolver_preparse

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 48e8992e33ab
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 10ba439968f7..f28ba8a703fe 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -83,7 +83,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
long ret;

ret = -EINVAL;
- if (plen > 1024 * 1024 - 1)
+ if (plen > 1024 * 1024 - 1 || plen < 48)
goto error;

/* draw all the data into kernel space */

[Edward Adam Davis]

please test slab-out-of-bounds Read in dns_resolver_preparse

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 48e8992e33ab

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 3233f4f25fed..15f19521021c 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -104,7 +104,7 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)

if (data[0] == 0) {
/* It may be a server list. */
- if (datalen <= sizeof(*bin))
+ if (datalen <= sizeof(*v1))
return -EINVAL;

bin = (const struct dns_payload_header *)data;

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+94bbb7...@syzkaller.appspotmail.com

Tested on:

commit: 48e8992e Add linux-next specific files for 20231213
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=12c0cb2ae80000

kernel config: https://syzkaller.appspot.com/x/.config?x=978b8aaa2e92a8f
dashboard link: https://syzkaller.appspot.com/bug?extid=94bbb75204a05da3d89f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=149ece7ce80000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

bin will be forcibly converted to "struct dns_server_list_v1_header *", so it
is necessary to compare datalen with sizeof(*v1).

Fixes: b946001d3bb1 ("keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry")

Reported-and-tested-by: syzbot+94bbb7...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
net/dns_resolver/dns_key.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+94bbb7...@syzkaller.appspotmail.com

Tested on:

commit: 48e8992e Add linux-next specific files for 20231213
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

console output: https://syzkaller.appspot.com/x/log.txt?x=156a0801e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=978b8aaa2e92a8f
dashboard link: https://syzkaller.appspot.com/bug?extid=94bbb75204a05da3d89f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=162b3ffee80000

[Edward Adam Davis]

--
2.43.0

[Simon Horman]

On Thu, Dec 14, 2023 at 10:46:10PM +0800, Edward Adam Davis wrote:
> bin will be forcibly converted to "struct dns_server_list_v1_header *", so it
> is necessary to compare datalen with sizeof(*v1).
>
> Fixes: b946001d3bb1 ("keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry")
> Reported-and-tested-by: syzbot+94bbb7...@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <ead...@qq.com>
> ---
> net/dns_resolver/dns_key.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

This change looks correct to me.
And I agree that it addresses a problem introduced by the cited commit.
I also note that it depends on the cited commit, which is not present in net.

Reviewed-by: Simon Horman <ho...@kernel.org>

[Jarkko Sakkinen]

Reviewed-by: Jarkko Sakkinen <jar...@kernel.org>

BR, Jarkko

[David Howells]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 2a6d363763a2..f18ca02aa95a 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -91,8 +91,6 @@ const struct cred *dns_resolver_cache;
static int
dns_resolver_preparse(struct key_preparsed_payload *prep)
{
- const struct dns_server_list_v1_header *v1;
- const struct dns_payload_header *bin;
struct user_key_payload *upayload;
unsigned long derrno;
int ret;
@@ -103,27 +101,28 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
return -EINVAL;

if (data[0] == 0) {

+ const struct dns_server_list_v1_header *v1;
+

/* It may be a server list. */
- if (datalen <= sizeof(*bin))
+ if (datalen <= sizeof(*v1))
return -EINVAL;

- bin = (const struct dns_payload_header *)data;
- kenter("[%u,%u],%u", bin->content, bin->version, datalen);
- if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) {
+ v1 = (const struct dns_server_list_v1_header *)data;
+ kenter("[%u,%u],%u", v1->hdr.content, v1->hdr.version, datalen);
+ if (v1->hdr.content != DNS_PAYLOAD_IS_SERVER_LIST) {
pr_warn_ratelimited(
"dns_resolver: Unsupported content type (%u)\n",
- bin->content);
+ v1->hdr.content);
return -EINVAL;
}

- if (bin->version != 1) {
+ if (v1->hdr.version != 1) {
pr_warn_ratelimited(
"dns_resolver: Unsupported server list version (%u)\n",
- bin->version);
+ v1->hdr.version);
return -EINVAL;
}

- v1 = (const struct dns_server_list_v1_header *)bin;
if ((v1->status != DNS_LOOKUP_GOOD &&
v1->status != DNS_LOOKUP_GOOD_WITH_BAD)) {
if (prep->expiry == TIME64_MAX)

[syzbot]

> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

want either no args or 2 args (repo, branch), got 5

[David Howells]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+94bbb7...@syzkaller.appspotmail.com

Tested on:

commit: 3f82f1c3 Merge tag 'x86-urgent-2023-12-23' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=132be7e9e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=9f7c7b3fa354ead9

dashboard link: https://syzkaller.appspot.com/bug?extid=94bbb75204a05da3d89f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=15ef6e26e80000