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

Thu Sep 26 08:53:42 UTC 2024

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.

BR, Jarkko