[PATCH 3.16.y-ckt 038/183] smack: fix possible use after frees in task_security() callers
From: Luis Henriques
Date: Fri Mar 06 2015 - 05:57:26 EST
3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
commit 6d1cff2a885850b78b40c34777b46cf5da5d1050 upstream.
We hit use after free on dereferncing pointer to task_smack struct in
smk_of_task() called from smack_task_to_inode().
task_security() macro uses task_cred_xxx() to get pointer to the task_smack.
task_cred_xxx() could be used only for non-pointer members of task's
credentials. It cannot be used for pointer members since what they point
to may disapper after dropping RCU read lock.
Mainly task_security() used this way:
smk_of_task(task_security(p))
Intead of this introduce function smk_of_task_struct() which
takes task_struct as argument and returns pointer to smk_known struct
and do this under RCU read lock.
Bogus task_security() macro is not used anymore, so remove it.
KASan's report for this:
AddressSanitizer: use after free in smack_task_to_inode+0x50/0x70 at addr c4635600
=============================================================================
BUG kmalloc-64 (Tainted: PO): kasan error
-----------------------------------------------------------------------------
Disabling lock debugging due to kernel taint
INFO: Allocated in new_task_smack+0x44/0xd8 age=39 cpu=0 pid=1866
kmem_cache_alloc_trace+0x88/0x1bc
new_task_smack+0x44/0xd8
smack_cred_prepare+0x48/0x21c
security_prepare_creds+0x44/0x4c
prepare_creds+0xdc/0x110
smack_setprocattr+0x104/0x150
security_setprocattr+0x4c/0x54
proc_pid_attr_write+0x12c/0x194
vfs_write+0x1b0/0x370
SyS_write+0x5c/0x94
ret_fast_syscall+0x0/0x48
INFO: Freed in smack_cred_free+0xc4/0xd0 age=27 cpu=0 pid=1564
kfree+0x270/0x290
smack_cred_free+0xc4/0xd0
security_cred_free+0x34/0x3c
put_cred_rcu+0x58/0xcc
rcu_process_callbacks+0x738/0x998
__do_softirq+0x264/0x4cc
do_softirq+0x94/0xf4
irq_exit+0xbc/0x120
handle_IRQ+0x104/0x134
gic_handle_irq+0x70/0xac
__irq_svc+0x44/0x78
_raw_spin_unlock+0x18/0x48
sync_inodes_sb+0x17c/0x1d8
sync_filesystem+0xac/0xfc
vdfs_file_fsync+0x90/0xc0
vfs_fsync_range+0x74/0x7c
INFO: Slab 0xd3b23f50 objects=32 used=31 fp=0xc4635600 flags=0x4080
INFO: Object 0xc4635600 @offset=5632 fp=0x (null)
Bytes b4 c46355f0: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
Object c4635600: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
Object c4635610: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
Object c4635620: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
Object c4635630: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk.
Redzone c4635640: bb bb bb bb ....
Padding c46356e8: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
Padding c46356f8: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
CPU: 5 PID: 834 Comm: launchpad_prelo Tainted: PBO 3.10.30 #1
Backtrace:
[<c00233a4>] (dump_backtrace+0x0/0x158) from [<c0023dec>] (show_stack+0x20/0x24)
r7:c4634010 r6:d3b23f50 r5:c4635600 r4:d1002140
[<c0023dcc>] (show_stack+0x0/0x24) from [<c06d6d7c>] (dump_stack+0x20/0x28)
[<c06d6d5c>] (dump_stack+0x0/0x28) from [<c01c1d50>] (print_trailer+0x124/0x144)
[<c01c1c2c>] (print_trailer+0x0/0x144) from [<c01c1e88>] (object_err+0x3c/0x44)
r7:c4635600 r6:d1002140 r5:d3b23f50 r4:c4635600
[<c01c1e4c>] (object_err+0x0/0x44) from [<c01cac18>] (kasan_report_error+0x2b8/0x538)
r6:d1002140 r5:d3b23f50 r4:c6429cf8 r3:c09e1aa7
[<c01ca960>] (kasan_report_error+0x0/0x538) from [<c01c9430>] (__asan_load4+0xd4/0xf8)
[<c01c935c>] (__asan_load4+0x0/0xf8) from [<c031e168>] (smack_task_to_inode+0x50/0x70)
r5:c4635600 r4:ca9da000
[<c031e118>] (smack_task_to_inode+0x0/0x70) from [<c031af64>] (security_task_to_inode+0x3c/0x44)
r5:cca25e80 r4:c0ba9780
[<c031af28>] (security_task_to_inode+0x0/0x44) from [<c023d614>] (pid_revalidate+0x124/0x178)
r6:00000000 r5:cca25e80 r4:cbabe3c0 r3:00008124
[<c023d4f0>] (pid_revalidate+0x0/0x178) from [<c01db98c>] (lookup_fast+0x35c/0x43y4)
r9:c6429efc r8:00000101 r7:c079d940 r6:c6429e90 r5:c6429ed8 r4:c83c4148
[<c01db630>] (lookup_fast+0x0/0x434) from [<c01deec8>] (do_last.isra.24+0x1c0/0x1108)
[<c01ded08>] (do_last.isra.24+0x0/0x1108) from [<c01dff04>] (path_openat.isra.25+0xf4/0x648)
[<c01dfe10>] (path_openat.isra.25+0x0/0x648) from [<c01e1458>] (do_filp_open+0x3c/0x88)
[<c01e141c>] (do_filp_open+0x0/0x88) from [<c01ccb28>] (do_sys_open+0xf0/0x198)
r7:00000001 r6:c0ea2180 r5:0000000b r4:00000000
[<c01cca38>] (do_sys_open+0x0/0x198) from [<c01ccc00>] (SyS_open+0x30/0x34)
[<c01ccbd0>] (SyS_open+0x0/0x34) from [<c001db80>] (ret_fast_syscall+0x0/0x48)
Read of size 4 by thread T834:
Memory state around the buggy address:
c4635380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
c4635400: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
c4635480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
c4635500: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
c4635580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>c4635600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
c4635680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
c4635700: 00 00 00 00 04 fc fc fc fc fc fc fc fc fc fc fc
c4635780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
c4635800: 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc fc
c4635880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
[ luis: backported to 3.16:
- dropped changes to smk_bu_task()
- adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
security/smack/smack.h | 10 ++++++++++
security/smack/smack_lsm.c | 20 +++++++++++---------
2 files changed, 21 insertions(+), 9 deletions(-)
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 020307ef0972..3bb1618f14b4 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -297,6 +297,16 @@ static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
return tsp->smk_task;
}
+static inline struct smack_known *smk_of_task_struct(const struct task_struct *t)
+{
+ struct smack_known *skp;
+
+ rcu_read_lock();
+ skp = smk_of_task(__task_cred(t)->security);
+ rcu_read_unlock();
+ return skp;
+}
+
/*
* Present a pointer to the forked smack label entry in an task blob.
*/
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index f2c30801ce41..40cdee62097e 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -43,8 +43,6 @@
#include <linux/binfmts.h>
#include "smack.h"
-#define task_security(task) (task_cred_xxx((task), security))
-
#define TRANS_TRUE "TRUE"
#define TRANS_TRUE_SIZE 4
@@ -199,7 +197,8 @@ static int smk_ptrace_rule_check(struct task_struct *tracer, char *tracee_label,
saip = &ad;
}
- tsp = task_security(tracer);
+ rcu_read_lock();
+ tsp = __task_cred(tracer)->security;
skp = smk_of_task(tsp);
if ((mode & PTRACE_MODE_ATTACH) &&
@@ -217,11 +216,14 @@ static int smk_ptrace_rule_check(struct task_struct *tracer, char *tracee_label,
if (saip)
smack_log(skp->smk_known, tracee_label, 0, rc, saip);
+ rcu_read_unlock();
return rc;
}
/* In case of rule==SMACK_PTRACE_DEFAULT or mode==PTRACE_MODE_READ */
rc = smk_tskacc(tsp, tracee_label, smk_ptrace_mode(mode), saip);
+
+ rcu_read_unlock();
return rc;
}
@@ -248,7 +250,7 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
if (rc != 0)
return rc;
- skp = smk_of_task(task_security(ctp));
+ skp = smk_of_task_struct(ctp);
rc = smk_ptrace_rule_check(current, skp->smk_known, mode, __func__);
return rc;
@@ -1639,7 +1641,7 @@ static int smk_curacc_on_task(struct task_struct *p, int access,
const char *caller)
{
struct smk_audit_info ad;
- struct smack_known *skp = smk_of_task(task_security(p));
+ struct smack_known *skp = smk_of_task_struct(p);
smk_ad_init(&ad, caller, LSM_AUDIT_DATA_TASK);
smk_ad_setfield_u_tsk(&ad, p);
@@ -1689,7 +1691,7 @@ static int smack_task_getsid(struct task_struct *p)
*/
static void smack_task_getsecid(struct task_struct *p, u32 *secid)
{
- struct smack_known *skp = smk_of_task(task_security(p));
+ struct smack_known *skp = smk_of_task_struct(p);
*secid = skp->smk_secid;
}
@@ -1796,7 +1798,7 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
{
struct smk_audit_info ad;
struct smack_known *skp;
- struct smack_known *tkp = smk_of_task(task_security(p));
+ struct smack_known *tkp = smk_of_task_struct(p);
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
smk_ad_setfield_u_tsk(&ad, p);
@@ -1844,7 +1846,7 @@ static int smack_task_wait(struct task_struct *p)
static void smack_task_to_inode(struct task_struct *p, struct inode *inode)
{
struct inode_smack *isp = inode->i_security;
- struct smack_known *skp = smk_of_task(task_security(p));
+ struct smack_known *skp = smk_of_task_struct(p);
isp->smk_inode = skp->smk_known;
}
@@ -2988,7 +2990,7 @@ unlockandout:
*/
static int smack_getprocattr(struct task_struct *p, char *name, char **value)
{
- struct smack_known *skp = smk_of_task(task_security(p));
+ struct smack_known *skp = smk_of_task_struct(p);
char *cp;
int slen;
--
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