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linux/security/apparmor/include
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GUO Zihua 9a95c5bfbf ima: Avoid blocking in RCU read-side critical section 
A panic happens in ima_match_policy:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
PGD 42f873067 P4D 0
Oops: 0000 [#1] SMP NOPTI
CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
Kdump: loaded Tainted: P
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
               BIOS 0.0.0 02/06/2015
RIP: 0010:ima_match_policy+0x84/0x450
Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
      7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
      f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
      44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
FS:  00007f5195b51740(0000)
GS:ff3e278b12d40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ima_get_action+0x22/0x30
 process_measurement+0xb0/0x830
 ? page_add_file_rmap+0x15/0x170
 ? alloc_set_pte+0x269/0x4c0
 ? prep_new_page+0x81/0x140
 ? simple_xattr_get+0x75/0xa0
 ? selinux_file_open+0x9d/0xf0
 ima_file_check+0x64/0x90
 path_openat+0x571/0x1720
 do_filp_open+0x9b/0x110
 ? page_counter_try_charge+0x57/0xc0
 ? files_cgroup_alloc_fd+0x38/0x60
 ? __alloc_fd+0xd4/0x250
 ? do_sys_open+0x1bd/0x250
 do_sys_open+0x1bd/0x250
 do_syscall_64+0x5d/0x1d0
 entry_SYSCALL_64_after_hwframe+0x65/0xca

Commit c7423dbdbc ("ima: Handle -ESTALE returned by
ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
RCU read-side critical section which contains kmalloc with GFP_KERNEL.
This implies a possible sleep and violates limitations of RCU read-side
critical sections on non-PREEMPT systems.

Sleeping within RCU read-side critical section might cause
synchronize_rcu() returning early and break RCU protection, allowing a
UAF to happen.

The root cause of this issue could be described as follows:
|	Thread A	|	Thread B	|
|			|ima_match_policy	|
|			|  rcu_read_lock	|
|ima_lsm_update_rule	|			|
|  synchronize_rcu	|			|
|			|    kmalloc(GFP_KERNEL)|
|			|      sleep		|
==> synchronize_rcu returns early
|  kfree(entry)		|			|
|			|    entry = entry->next|
==> UAF happens and entry now becomes NULL (or could be anything).
|			|    entry->action	|
==> Accessing entry might cause panic.

To fix this issue, we are converting all kmalloc that is called within
RCU read-side critical section to use GFP_ATOMIC.

Fixes: c7423dbdbc ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
Cc: stable@vger.kernel.org
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
Signed-off-by: Paul Moore <paul@paul-moore.com>
2024-06-13 14:26:50 -04:00
..
apparmor.h apparmor: add io_uring mediation 2023-10-18 15:58:49 -07:00
apparmorfs.h apparmor: make export of raw binary profile to userspace optional 2022-07-09 15:13:59 -07:00
audit.h ima: Avoid blocking in RCU read-side critical section 2024-06-13 14:26:50 -04:00
capability.h apparmor: pass cred through to audit info. 2023-10-18 15:30:38 -07:00
cred.h apparmor: Simplify obtain the newest label on a cred 2022-10-03 14:49:04 -07:00
crypto.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
domain.h apparmor: extend permissions to support a label and tag string 2022-10-03 14:49:03 -07:00
file.h apparmor: pass cred through to audit info. 2023-10-18 15:30:38 -07:00
ipc.h apparmor: pass cred through to audit info. 2023-10-18 15:30:38 -07:00
label.h apparmor: refactor profile rules and attachments 2022-10-03 14:49:04 -07:00
lib.h apparmor: refcount the pdb 2023-10-18 15:30:47 -07:00
match.h apparmor: refcount the pdb 2023-10-18 15:30:47 -07:00
mount.h apparmor: Fix regression in mount mediation 2023-10-18 16:01:32 -07:00
net.h apparmor: pass cred through to audit info. 2023-10-18 15:30:38 -07:00
path.h apparmor: allow label to carry debug flags 2022-07-19 02:55:45 -07:00
perms.h apparmor: add io_uring mediation 2023-10-18 15:58:49 -07:00
policy_compat.h apparmor: isolate policy backwards compatibility to its own file 2022-10-03 14:49:03 -07:00
policy_ns.h apparmor: remove unused functions in policy_ns.c/.h 2023-10-15 21:44:31 -07:00
policy_unpack.h + Features 2022-12-14 13:42:09 -08:00
policy.h apparmor: allow restricting unprivileged change_profile 2023-10-18 15:48:44 -07:00
procattr.h AppArmor: Add selfattr hooks 2023-11-12 22:54:42 -05:00
resource.h apparmor: pass cred through to audit info. 2023-10-18 15:30:38 -07:00
secid.h apparmor: disable showing the mode as part of a secid to secctx 2022-07-13 17:18:29 -07:00
sig_names.h apparmor: audit unknown signal numbers 2018-02-09 11:30:01 -08:00
task.h apparmor: add user namespace creation mediation 2023-10-18 15:49:02 -07:00