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
ima_file_check+0x64/0x90
path_openat+0x571/0x1720
do_filp_open+0x9b/0x110
do_sys_open+0x1bd/0x250
do_syscall_64+0x5d/0x1d0
entry_SYSCALL_64_after_hwframe+0x65/0xca
(stack trace marked with ? is deleted)
Commit c7423dbdbc9e ("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: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: GUO Zihua <guozihua@xxxxxxxxxx>
---
security/integrity/ima/ima_policy.c | 2 +-
security/selinux/ss/services.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index c0556907c2e6..c0cf9b6a01f0 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -410,7 +410,7 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
* Immutable elements are copied over as pointers and data; only
* lsm rules can change
*/
- nentry = kmemdup(entry, sizeof(*nentry), GFP_KERNEL);
+ nentry = kmemdup(entry, sizeof(*nentry), GFP_ATOMIC);
if (!nentry)
return NULL;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index e88b1b6c4adb..b7cfad1a2964 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -3549,7 +3549,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
return -EINVAL;
}
- tmprule = kzalloc(sizeof(struct selinux_audit_rule), GFP_KERNEL);
+ tmprule = kzalloc(sizeof(struct selinux_audit_rule), GFP_ATOMIC);
if (!tmprule)
return -ENOMEM;
context_init(&tmprule->au_ctxt);
--
2.34.1
