[PATCH] security/keys: fix slab-out-of-bounds in key_task_permission

Thu Sep 26 08:55:31 UTC 2024

On Thu Sep 26, 2024 at 11:53 AM EEST, Jarkko Sakkinen wrote:
> On Thu Sep 26, 2024 at 6:48 AM EEST, Chen Ridong wrote:
> >
> > On 2024/9/19 4:57, Jarkko Sakkinen wrote:
> > > On Wed Sep 18, 2024 at 10:30 AM EEST, Chen Ridong wrote:
> > >>
> > >>
> > >> On 2024/9/15 21:59, Jarkko Sakkinen wrote:
> > >>> On Sun Sep 15, 2024 at 3:55 AM EEST, Chen Ridong wrote:
> > >>>>
> > >>>>
> > >>>> On 2024/9/14 19:33, Jarkko Sakkinen wrote:
> > >>>>> On Fri Sep 13, 2024 at 10:09 AM EEST, Chen Ridong wrote:
> > >>>>>> We meet the same issue with the LINK, which reads memory out of bounds:
> > >>>>>
> > >>>>> Nit: don't use "we" anywhere".
> > >>>>>
> > >>>>> Tbh, I really don't understand the sentence above. I don't what
> > >>>>> "the same issue with the LINK" really is.
> > >>>>>
> > >>>>
> > >>>> Hello, Jarkko.
> > >>>> I apologize for any confusion caused.
> > >>>>
> > >>>> I've encountered a bug reported by syzkaller. I also found the same bug
> > >>>> reported at this LINK:
> > >>>> https://syzkaller.appspot.com/bug?id=68a5e206c2a8e08d317eb83f05610c0484ad10b9.
> > >>>>
> > >>>>>> BUG: KASAN: slab-out-of-bounds in __kuid_val include/linux/uidgid.h:36
> > >>>>>> BUG: KASAN: slab-out-of-bounds in uid_eq include/linux/uidgid.h:63 [inline]
> > >>>>>> BUG: KASAN: slab-out-of-bounds in key_task_permission+0x394/0x410
> > >>>>>> security/keys/permission.c:54
> > >>>>>> Read of size 4 at addr ffff88813c3ab618 by task stress-ng/4362
> > >>>>>>
> > >>>>>> CPU: 2 PID: 4362 Comm: stress-ng Not tainted 5.10.0-14930-gafbffd6c3ede #15
> > >>>>>> Call Trace:
> > >>>>>>     __dump_stack lib/dump_stack.c:82 [inline]
> > >>>>>>     dump_stack+0x107/0x167 lib/dump_stack.c:123
> > >>>>>>     print_address_description.constprop.0+0x19/0x170 mm/kasan/report.c:400
> > >>>>>>     __kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560
> > >>>>>>     kasan_report+0x3a/0x50 mm/kasan/report.c:585
> > >>>>>>     __kuid_val include/linux/uidgid.h:36 [inline]
> > >>>>>>     uid_eq include/linux/uidgid.h:63 [inline]
> > >>>>>>     key_task_permission+0x394/0x410 security/keys/permission.c:54
> > >>>>>>     search_nested_keyrings+0x90e/0xe90 security/keys/keyring.c:793
> > >>>>>>     keyring_search_rcu+0x1b6/0x310 security/keys/keyring.c:922
> > >>>>>>     search_cred_keyrings_rcu+0x111/0x2e0 security/keys/process_keys.c:459
> > >>>>>>     search_process_keyrings_rcu+0x1d/0x310 security/keys/process_keys.c:544
> > >>>>>>     lookup_user_key+0x782/0x12e0 security/keys/process_keys.c:762
> > >>>>>>     keyctl_invalidate_key+0x20/0x190 security/keys/keyctl.c:434
> > >>>>>>     __do_sys_keyctl security/keys/keyctl.c:1978 [inline]
> > >>>>>>     __se_sys_keyctl+0x1de/0x5b0 security/keys/keyctl.c:1880
> > >>>>>>     do_syscall_64+0x30/0x40 arch/x86/entry/common.c:46
> > >>>>>>     entry_SYSCALL_64_after_hwframe+0x67/0xd1
> > >>>>>>
> > >>>>>> However, we can't reproduce this issue.
> > >>>>>
> > >>>>> "The issue cannot be easily reproduced but by analyzing the code
> > >>>>> it can be broken into following steps:"
> > >>>>
> > >>>> Thank you for your correction.
> > >>>> Does this patch address the issue correctly? Is this patch acceptable?
> > >>>
> > >>> I only comment new patch versions so not giving any promises but I can
> > >>> say that it is I think definitely in the correct direction :-)
> > >>>
> > >>> BR, Jarkko
> > >>
> > >> Hello, Jarkko. I have reproduced this issue. It can be reproduced by
> > >> following these steps:
> > >>
> > >> 1. Add the helper patch.
> > >>
> > >> @@ -205,6 +205,9 @@ static void hash_key_type_and_desc(struct
> > >> keyring_index_key *index_key)
> > >>           else if (index_key->type == &key_type_keyring && (hash &
> > >> fan_mask) != 0)
> > >>                   hash = (hash + (hash << level_shift)) & ~fan_mask;
> > >>           index_key->hash = hash;
> > >> +       if ((index_key->hash & 0xff) == 0xe6) {
> > >> +                       pr_err("hash_key_type_and_desc: type %s %s
> > >> 0x%x\n",  index_key->type->name, index_key->description, index_key->hash);
> > >> +       }
> > >>    }
> > >>
> > >> 2. Pick up the inputs whose hash is xxe6 using the following cmd. If a
> > >> key's hash is xxe6, it will be printed.
> > >>
> > >> for ((i=0; i<=10000; i++)); do ./test_key user user$i "Some payload"; done
> > >>
> > >> You have complile test_key whith following code.
> > >>
> > >> #include <sys/types.h>
> > >> #include <keyutils.h>
> > >> #include <stdint.h>
> > >> #include <stdio.h>
> > >> #include <stdlib.h>
> > >> #include <string.h>
> > >>
> > >> int
> > >> main(int argc, char *argv[])
> > >> {
> > >>      key_serial_t key;
> > >>
> > >>      if (argc != 4) {
> > >> 	   fprintf(stderr, "Usage: %s type description payload\n",
> > >> 			   argv[0]);
> > >> 	   exit(EXIT_FAILURE);
> > >>      }
> > >>
> > >>      key = add_key(argv[1], argv[2], argv[3], strlen(argv[3]),
> > >> 			   KEY_SPEC_SESSION_KEYRING);
> > >>      if (key == -1) {
> > >> 	   perror("add_key");
> > >> 	   exit(EXIT_FAILURE);
> > >>      }
> > >>
> > >>      printf("Key ID is %jx\n", (uintmax_t) key);
> > >>
> > >>      exit(EXIT_SUCCESS);
> > >> }
> > >>
> > >>
> > >> 3. Have more than 32 inputs now. their hashes are xxe6.
> > >> eg.
> > >> hash_key_type_and_desc: type user user438 0xe3033fe6
> > >> hash_key_type_and_desc: type user user526 0xeb7eade6
> > >> ...
> > >> hash_key_type_and_desc: type user user9955 0x44bc99e6
> > >>
> > >> 4. Reboot and add the keys obtained from step 3.
> > >> When adding keys to the ROOT that their hashes are all xxe6, and up to
> > >> 16, the ROOT has keys with hashes that are not xxe6 (e.g., slot 0), so
> > >> the keys are dissimilar. The ROOT will then split NODE A without using a
> > >> shortcut. When NODE A is filled with keys that have hashes of xxe6, the
> > >> keys are similar. NODE A will split with a shortcut.
> > >>
> > >> As my analysis, if a slot of the root is a shortcut(slot 6), it may be
> > >> mistakenly be transferred to a key*, leading to an read out-of-bounds read.
> > >>
> > >>                         NODE A
> > >>                 +------>+---+
> > >>         ROOT    |       | 0 | xxe6
> > >>         +---+   |       +---+
> > >>    xxxx | 0 | shortcut  :   : xxe6
> > >>         +---+   |       +---+
> > >>    xxe6 :   :   |       |   | xxe6
> > >>         +---+   |       +---+
> > >>         | 6 |---+       :   : xxe6
> > >>         +---+           +---+
> > >>    xxe6 :   :           | f | xxe6
> > >>         +---+           +---+
> > >>    xxe6 | f |
> > >>         +---+
> > >>
> > >> 5. cat /proc/keys. and the issue is reproduced.
> > > 
> > > Hi, I'll try to run through your procedure next week and give my comments.
> > > Thanks for doing this.
> > > 
> > > BR, Jarkko
> >
> > Hi, Jarkko, have you run these procedure?
> > I have tested this patch with LTP and a pressure test(stress-ng --key), 
> > and this patch have fixed this issue. Additionally, no new bugs have 
> > been found so far.
> >
> > I am looking forward to your reply.
> >
> > Best regards,
> > Ridong
>
> Nope because we are apparently stuck with release critical bug:
>
> https://lore.kernel.org/linux-integrity/D4EPMF7G3E05.1VHS9CVG3DZDE@kernel.org/T/#t
>
> Might take several weeks before I look into this.

I was expecting to send a PR early this week since the patch set
addresses the issue so thus wrong estimation.

BR, Jarkko