linux/security, branch v3.13

SELinux: Fix possible NULL pointer dereference in selinux_inode_permission()

2014-01-12T09:53:13Z

While running stress tests on adding and deleting ftrace instances I hit this bug: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 IP: selinux_inode_permission+0x85/0x160 PGD 63681067 PUD 7ddbe067 PMD 0 Oops: 0000 [#1] PREEMPT CPU: 0 PID: 5634 Comm: ftrace-test-mki Not tainted 3.13.0-rc4-test-00033-gd2a6dde-dirty #20 Hardware name: /DG965MQ, BIOS MQ96510J.86A.0372.2006.0605.1717 06/05/2006 task: ffff880078375800 ti: ffff88007ddb0000 task.ti: ffff88007ddb0000 RIP: 0010:[] [] selinux_inode_permission+0x85/0x160 RSP: 0018:ffff88007ddb1c48 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000800000 RCX: ffff88006dd43840 RDX: 0000000000000001 RSI: 0000000000000081 RDI: ffff88006ee46000 RBP: ffff88007ddb1c88 R08: 0000000000000000 R09: ffff88007ddb1c54 R10: 6e6576652f6f6f66 R11: 0000000000000003 R12: 0000000000000000 R13: 0000000000000081 R14: ffff88006ee46000 R15: 0000000000000000 FS: 00007f217b5b6700(0000) GS:ffffffff81e21000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033^M CR2: 0000000000000020 CR3: 000000006a0fe000 CR4: 00000000000007f0 Call Trace: security_inode_permission+0x1c/0x30 __inode_permission+0x41/0xa0 inode_permission+0x18/0x50 link_path_walk+0x66/0x920 path_openat+0xa6/0x6c0 do_filp_open+0x43/0xa0 do_sys_open+0x146/0x240 SyS_open+0x1e/0x20 system_call_fastpath+0x16/0x1b Code: 84 a1 00 00 00 81 e3 00 20 00 00 89 d8 83 c8 02 40 f6 c6 04 0f 45 d8 40 f6 c6 08 74 71 80 cf 02 49 8b 46 38 4c 8d 4d cc 45 31 c0 <0f> b7 50 20 8b 70 1c 48 8b 41 70 89 d9 8b 78 04 e8 36 cf ff ff RIP selinux_inode_permission+0x85/0x160 CR2: 0000000000000020 Investigating, I found that the inode->i_security was NULL, and the dereference of it caused the oops. in selinux_inode_permission(): isec = inode->i_security; rc = avc_has_perm_noaudit(sid, isec->sid, isec->sclass, perms, 0, &avd); Note, the crash came from stressing the deletion and reading of debugfs files. I was not able to recreate this via normal files. But I'm not sure they are safe. It may just be that the race window is much harder to hit. What seems to have happened (and what I have traced), is the file is being opened at the same time the file or directory is being deleted. As the dentry and inode locks are not held during the path walk, nor is the inodes ref counts being incremented, there is nothing saving these structures from being discarded except for an rcu_read_lock(). The rcu_read_lock() protects against freeing of the inode, but it does not protect freeing of the inode_security_struct. Now if the freeing of the i_security happens with a call_rcu(), and the i_security field of the inode is not changed (it gets freed as the inode gets freed) then there will be no issue here. (Linus Torvalds suggested not setting the field to NULL such that we do not need to check if it is NULL in the permission check). Note, this is a hack, but it fixes the problem at hand. A real fix is to restructure the destroy_inode() to call all the destructor handlers from the RCU callback. But that is a major job to do, and requires a lot of work. For now, we just band-aid this bug with this fix (it works), and work on a more maintainable solution in the future. Link: http://lkml.kernel.org/r/20140109101932.0508dec7@gandalf.local.home Link: http://lkml.kernel.org/r/20140109182756.17abaaa8@gandalf.local.home Cc: stable@vger.kernel.org Signed-off-by: Steven Rostedt Signed-off-by: Linus Torvalds

selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock()

2013-12-23T22:45:17Z

selinux_setprocattr() does ptrace_parent(p) under task_lock(p), but task_struct->alloc_lock doesn't pin ->parent or ->ptrace, this looks confusing and triggers the "suspicious RCU usage" warning because ptrace_parent() does rcu_dereference_check(). And in theory this is wrong, spin_lock()->preempt_disable() doesn't necessarily imply rcu_read_lock() we need to access the ->parent. Reported-by: Evan McNabb Signed-off-by: Oleg Nesterov Cc: stable@vger.kernel.org Signed-off-by: Paul Moore

selinux: fix broken peer recv check

2013-12-23T22:45:17Z

Fix a broken networking check. Return an error if peer recv fails. If secmark is active and the packet recv succeeds the peer recv error is ignored. Signed-off-by: Chad Hanson Cc: stable@vger.kernel.org Signed-off-by: Paul Moore

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

2013-12-15T19:28:02Z

Pull SELinux fixes from James Morris. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: selinux: process labeled IPsec TCP SYN-ACK packets properly in selinux_ip_postroute() selinux: look for IPsec labels on both inbound and outbound packets selinux: handle TCP SYN-ACK packets correctly in selinux_ip_postroute() selinux: handle TCP SYN-ACK packets correctly in selinux_ip_output() selinux: fix possible memory leak

Revert "selinux: consider filesystem subtype in policies"

2013-12-15T19:17:45Z

This reverts commit 102aefdda4d8275ce7d7100bc16c88c74272b260. Tom London reports that it causes sync() to hang on Fedora rawhide: https://bugzilla.redhat.com/show_bug.cgi?id=1033965 and Josh Boyer bisected it down to this commit. Reverting the commit in the rawhide kernel fixes the problem. Eric Paris root-caused it to incorrect subtype matching in that commit breaking fuse, and has a tentative patch, but by now we're better off retrying this in 3.14 rather than playing with it any more. Reported-by: Tom London Bisected-by: Josh Boyer Acked-by: Eric Paris Cc: James Morris Cc: Anand Avati Cc: Paul Moore Signed-off-by: Linus Torvalds

Merge branch 'master' of git://git.infradead.org/users/pcmoore/selinux_fixes into for-linus

2013-12-13T02:27:55Z

selinux: process labeled IPsec TCP SYN-ACK packets properly in selinux_ip_postroute()

2013-12-12T22:21:31Z

Due to difficulty in arriving at the proper security label for TCP SYN-ACK packets in selinux_ip_postroute(), we need to check packets while/before they are undergoing XFRM transforms instead of waiting until afterwards so that we can determine the correct security label. Reported-by: Janak Desai Cc: stable@vger.kernel.org Signed-off-by: Paul Moore

selinux: look for IPsec labels on both inbound and outbound packets

2013-12-12T22:21:31Z

Previously selinux_skb_peerlbl_sid() would only check for labeled IPsec security labels on inbound packets, this patch enables it to check both inbound and outbound traffic for labeled IPsec security labels. Reported-by: Janak Desai Cc: stable@vger.kernel.org Signed-off-by: Paul Moore

selinux: handle TCP SYN-ACK packets correctly in selinux_ip_postroute()

2013-12-12T22:21:31Z

In selinux_ip_postroute() we perform access checks based on the packet's security label. For locally generated traffic we get the packet's security label from the associated socket; this works in all cases except for TCP SYN-ACK packets. In the case of SYN-ACK packet's the correct security label is stored in the connection's request_sock, not the server's socket. Unfortunately, at the point in time when selinux_ip_postroute() is called we can't query the request_sock directly, we need to recreate the label using the same logic that originally labeled the associated request_sock. See the inline comments for more explanation. Reported-by: Janak Desai Tested-by: Janak Desai Cc: stable@vger.kernel.org Signed-off-by: Paul Moore

selinux: handle TCP SYN-ACK packets correctly in selinux_ip_output()

2013-12-12T22:21:31Z

In selinux_ip_output() we always label packets based on the parent socket. While this approach works in almost all cases, it doesn't work in the case of TCP SYN-ACK packets when the correct label is not the label of the parent socket, but rather the label of the larval socket represented by the request_sock struct. Unfortunately, since the request_sock isn't queued on the parent socket until *after* the SYN-ACK packet is sent, we can't lookup the request_sock to determine the correct label for the packet; at this point in time the best we can do is simply pass/NF_ACCEPT the packet. It must be said that simply passing the packet without any explicit labeling action, while far from ideal, is not terrible as the SYN-ACK packet will inherit any IP option based labeling from the initial connection request so the label *should* be correct and all our access controls remain in place so we shouldn't have to worry about information leaks. Reported-by: Janak Desai Tested-by: Janak Desai Cc: stable@vger.kernel.org Signed-off-by: Paul Moore