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smack: fix possible use after frees in task_security() callers
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@samsung.com> Cc: <stable@vger.kernel.org>
This commit is contained in:
Andrey Ryabinin
Casey Schaufler
parent
138a868f00
commit
6d1cff2a88
@ -299,6 +299,16 @@ static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
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return tsp->smk_task;
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}
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static inline struct smack_known *smk_of_task_struct(const struct task_struct *t)
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{
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struct smack_known *skp;
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rcu_read_lock();
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skp = smk_of_task(__task_cred(t)->security);
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rcu_read_unlock();
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return skp;
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}
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/*
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* Present a pointer to the forked smack label entry in an task blob.
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*/
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@ -43,8 +43,6 @@
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#include <linux/binfmts.h>
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#include "smack.h"
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#define task_security(task) (task_cred_xxx((task), security))
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#define TRANS_TRUE "TRUE"
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#define TRANS_TRUE_SIZE 4
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@ -123,7 +121,7 @@ static int smk_bu_current(char *note, struct smack_known *oskp,
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static int smk_bu_task(struct task_struct *otp, int mode, int rc)
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{
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struct task_smack *tsp = current_security();
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struct task_smack *otsp = task_security(otp);
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struct smack_known *smk_task = smk_of_task_struct(otp);
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char acc[SMK_NUM_ACCESS_TYPE + 1];
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if (rc <= 0)
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@ -131,7 +129,7 @@ static int smk_bu_task(struct task_struct *otp, int mode, int rc)
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smk_bu_mode(mode, acc);
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pr_info("Smack Bringup: (%s %s %s) %s to %s\n",
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tsp->smk_task->smk_known, otsp->smk_task->smk_known, acc,
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tsp->smk_task->smk_known, smk_task->smk_known, acc,
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current->comm, otp->comm);
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return 0;
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}
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@ -352,7 +350,8 @@ static int smk_ptrace_rule_check(struct task_struct *tracer,
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saip = &ad;
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}
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tsp = task_security(tracer);
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rcu_read_lock();
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tsp = __task_cred(tracer)->security;
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tracer_known = smk_of_task(tsp);
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if ((mode & PTRACE_MODE_ATTACH) &&
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@ -372,11 +371,14 @@ static int smk_ptrace_rule_check(struct task_struct *tracer,
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tracee_known->smk_known,
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0, rc, saip);
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rcu_read_unlock();
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return rc;
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}
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/* In case of rule==SMACK_PTRACE_DEFAULT or mode==PTRACE_MODE_READ */
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rc = smk_tskacc(tsp, tracee_known, smk_ptrace_mode(mode), saip);
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rcu_read_unlock();
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return rc;
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}
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@ -403,7 +405,7 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
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if (rc != 0)
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return rc;
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skp = smk_of_task(task_security(ctp));
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skp = smk_of_task_struct(ctp);
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rc = smk_ptrace_rule_check(current, skp, mode, __func__);
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return rc;
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@ -1830,7 +1832,7 @@ static int smk_curacc_on_task(struct task_struct *p, int access,
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const char *caller)
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{
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struct smk_audit_info ad;
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struct smack_known *skp = smk_of_task(task_security(p));
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struct smack_known *skp = smk_of_task_struct(p);
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int rc;
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smk_ad_init(&ad, caller, LSM_AUDIT_DATA_TASK);
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@ -1883,7 +1885,7 @@ static int smack_task_getsid(struct task_struct *p)
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*/
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static void smack_task_getsecid(struct task_struct *p, u32 *secid)
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{
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struct smack_known *skp = smk_of_task(task_security(p));
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struct smack_known *skp = smk_of_task_struct(p);
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*secid = skp->smk_secid;
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}
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@ -1990,7 +1992,7 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
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{
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struct smk_audit_info ad;
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struct smack_known *skp;
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struct smack_known *tkp = smk_of_task(task_security(p));
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struct smack_known *tkp = smk_of_task_struct(p);
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int rc;
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smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
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@ -2044,7 +2046,7 @@ static int smack_task_wait(struct task_struct *p)
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static void smack_task_to_inode(struct task_struct *p, struct inode *inode)
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{
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struct inode_smack *isp = inode->i_security;
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struct smack_known *skp = smk_of_task(task_security(p));
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struct smack_known *skp = smk_of_task_struct(p);
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isp->smk_inode = skp;
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}
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@ -3226,7 +3228,7 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
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*/
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static int smack_getprocattr(struct task_struct *p, char *name, char **value)
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{
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struct smack_known *skp = smk_of_task(task_security(p));
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struct smack_known *skp = smk_of_task_struct(p);
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char *cp;
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int slen;
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