From 6d1cff2a885850b78b40c34777b46cf5da5d1050 Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Tue, 13 Jan 2015 18:52:40 +0300 Subject: 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: [] (dump_backtrace+0x0/0x158) from [] (show_stack+0x20/0x24) r7:c4634010 r6:d3b23f50 r5:c4635600 r4:d1002140 [] (show_stack+0x0/0x24) from [] (dump_stack+0x20/0x28) [] (dump_stack+0x0/0x28) from [] (print_trailer+0x124/0x144) [] (print_trailer+0x0/0x144) from [] (object_err+0x3c/0x44) r7:c4635600 r6:d1002140 r5:d3b23f50 r4:c4635600 [] (object_err+0x0/0x44) from [] (kasan_report_error+0x2b8/0x538) r6:d1002140 r5:d3b23f50 r4:c6429cf8 r3:c09e1aa7 [] (kasan_report_error+0x0/0x538) from [] (__asan_load4+0xd4/0xf8) [] (__asan_load4+0x0/0xf8) from [] (smack_task_to_inode+0x50/0x70) r5:c4635600 r4:ca9da000 [] (smack_task_to_inode+0x0/0x70) from [] (security_task_to_inode+0x3c/0x44) r5:cca25e80 r4:c0ba9780 [] (security_task_to_inode+0x0/0x44) from [] (pid_revalidate+0x124/0x178) r6:00000000 r5:cca25e80 r4:cbabe3c0 r3:00008124 [] (pid_revalidate+0x0/0x178) from [] (lookup_fast+0x35c/0x43y4) r9:c6429efc r8:00000101 r7:c079d940 r6:c6429e90 r5:c6429ed8 r4:c83c4148 [] (lookup_fast+0x0/0x434) from [] (do_last.isra.24+0x1c0/0x1108) [] (do_last.isra.24+0x0/0x1108) from [] (path_openat.isra.25+0xf4/0x648) [] (path_openat.isra.25+0x0/0x648) from [] (do_filp_open+0x3c/0x88) [] (do_filp_open+0x0/0x88) from [] (do_sys_open+0xf0/0x198) r7:00000001 r6:c0ea2180 r5:0000000b r4:00000000 [] (do_sys_open+0x0/0x198) from [] (SyS_open+0x30/0x34) [] (SyS_open+0x0/0x34) from [] (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 Cc: --- security/smack/smack.h | 10 ++++++++++ security/smack/smack_lsm.c | 24 +++++++++++++----------- 2 files changed, 23 insertions(+), 11 deletions(-) (limited to 'security/smack') diff --git a/security/smack/smack.h b/security/smack/smack.h index 7629eaeb1fb2..67ccb7b2b89b 100644 --- a/security/smack/smack.h +++ b/security/smack/smack.h @@ -299,6 +299,16 @@ 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 f60ded3a8da1..a0ccce4e46f8 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -43,8 +43,6 @@ #include #include "smack.h" -#define task_security(task) (task_cred_xxx((task), security)) - #define TRANS_TRUE "TRUE" #define TRANS_TRUE_SIZE 4 @@ -123,7 +121,7 @@ static int smk_bu_current(char *note, struct smack_known *oskp, static int smk_bu_task(struct task_struct *otp, int mode, int rc) { struct task_smack *tsp = current_security(); - struct task_smack *otsp = task_security(otp); + struct smack_known *smk_task = smk_of_task_struct(otp); char acc[SMK_NUM_ACCESS_TYPE + 1]; if (rc <= 0) @@ -131,7 +129,7 @@ static int smk_bu_task(struct task_struct *otp, int mode, int rc) smk_bu_mode(mode, acc); pr_info("Smack Bringup: (%s %s %s) %s to %s\n", - tsp->smk_task->smk_known, otsp->smk_task->smk_known, acc, + tsp->smk_task->smk_known, smk_task->smk_known, acc, current->comm, otp->comm); return 0; } @@ -352,7 +350,8 @@ static int smk_ptrace_rule_check(struct task_struct *tracer, saip = &ad; } - tsp = task_security(tracer); + rcu_read_lock(); + tsp = __task_cred(tracer)->security; tracer_known = smk_of_task(tsp); if ((mode & PTRACE_MODE_ATTACH) && @@ -372,11 +371,14 @@ static int smk_ptrace_rule_check(struct task_struct *tracer, tracee_known->smk_known, 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_known, smk_ptrace_mode(mode), saip); + + rcu_read_unlock(); return rc; } @@ -403,7 +405,7 @@ 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, mode, __func__); return rc; @@ -1830,7 +1832,7 @@ 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); int rc; smk_ad_init(&ad, caller, LSM_AUDIT_DATA_TASK); @@ -1883,7 +1885,7 @@ 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; } @@ -1990,7 +1992,7 @@ 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); int rc; smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK); @@ -2044,7 +2046,7 @@ 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; } @@ -3226,7 +3228,7 @@ 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; -- cgit v1.2.3-59-g8ed1b