user/sven/linux.git/security, branch v3.12.34

selinux: fix inode security list corruption

2014-11-13T18:02:18Z

commit 923190d32de4428afbea5e5773be86bea60a9925 upstream. sb_finish_set_opts() can race with inode_free_security() when initializing inode security structures for inodes created prior to initial policy load or by the filesystem during ->mount(). This appears to have always been a possible race, but commit 3dc91d4 ("SELinux: Fix possible NULL pointer dereference in selinux_inode_permission()") made it more evident by immediately reusing the unioned list/rcu element of the inode security structure for call_rcu() upon an inode_free_security(). But the underlying issue was already present before that commit as a possible use-after-free of isec. Shivnandan Kumar reported the list corruption and proposed a patch to split the list and rcu elements out of the union as separate fields of the inode_security_struct so that setting the rcu element would not affect the list element. However, this would merely hide the issue and not truly fix the code. This patch instead moves up the deletion of the list entry prior to dropping the sbsec->isec_lock initially. Then, if the inode is dropped subsequently, there will be no further references to the isec. Reported-by: Shivnandan Kumar Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore Signed-off-by: Jiri Slaby

evm: check xattr value length and type in evm_inode_setxattr()

2014-11-13T18:02:14Z

commit 3b1deef6b1289a99505858a3b212c5b50adf0c2f upstream. evm_inode_setxattr() can be called with no value. The function does not check the length so that following command can be used to produce the kernel oops: setfattr -n security.evm FOO. This patch fixes it. Changes in v3: * there is no reason to return different error codes for EVM_XATTR_HMAC and non EVM_XATTR_HMAC. Remove unnecessary test then. Changes in v2: * testing for validity of xattr type [ 1106.396921] BUG: unable to handle kernel NULL pointer dereference at (null) [ 1106.398192] IP: [] evm_inode_setxattr+0x2a/0x48 [ 1106.399244] PGD 29048067 PUD 290d7067 PMD 0 [ 1106.399953] Oops: 0000 [#1] SMP [ 1106.400020] Modules linked in: bridge stp llc evdev serio_raw i2c_piix4 button fuse [ 1106.400020] CPU: 0 PID: 3635 Comm: setxattr Not tainted 3.16.0-kds+ #2936 [ 1106.400020] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 1106.400020] task: ffff8800291a0000 ti: ffff88002917c000 task.ti: ffff88002917c000 [ 1106.400020] RIP: 0010:[] [] evm_inode_setxattr+0x2a/0x48 [ 1106.400020] RSP: 0018:ffff88002917fd50 EFLAGS: 00010246 [ 1106.400020] RAX: 0000000000000000 RBX: ffff88002917fdf8 RCX: 0000000000000000 [ 1106.400020] RDX: 0000000000000000 RSI: ffffffff818136d3 RDI: ffff88002917fdf8 [ 1106.400020] RBP: ffff88002917fd68 R08: 0000000000000000 R09: 00000000003ec1df [ 1106.400020] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800438a0a00 [ 1106.400020] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 1106.400020] FS: 00007f7dfa7d7740(0000) GS:ffff88005da00000(0000) knlGS:0000000000000000 [ 1106.400020] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1106.400020] CR2: 0000000000000000 CR3: 000000003763e000 CR4: 00000000000006f0 [ 1106.400020] Stack: [ 1106.400020] ffff8800438a0a00 ffff88002917fdf8 0000000000000000 ffff88002917fd98 [ 1106.400020] ffffffff812a1030 ffff8800438a0a00 ffff88002917fdf8 0000000000000000 [ 1106.400020] 0000000000000000 ffff88002917fde0 ffffffff8116d08a ffff88002917fdc8 [ 1106.400020] Call Trace: [ 1106.400020] [] security_inode_setxattr+0x5d/0x6a [ 1106.400020] [] vfs_setxattr+0x6b/0x9f [ 1106.400020] [] setxattr+0x122/0x16c [ 1106.400020] [] ? mnt_want_write+0x21/0x45 [ 1106.400020] [] ? __sb_start_write+0x10f/0x143 [ 1106.400020] [] ? mnt_want_write+0x21/0x45 [ 1106.400020] [] ? __mnt_want_write+0x48/0x4f [ 1106.400020] [] SyS_setxattr+0x6e/0xb0 [ 1106.400020] [] system_call_fastpath+0x16/0x1b [ 1106.400020] Code: c3 0f 1f 44 00 00 55 48 89 e5 41 55 49 89 d5 41 54 49 89 fc 53 48 89 f3 48 c7 c6 d3 36 81 81 48 89 df e8 18 22 04 00 85 c0 75 07 <41> 80 7d 00 02 74 0d 48 89 de 4c 89 e7 e8 5a fe ff ff eb 03 83 [ 1106.400020] RIP [] evm_inode_setxattr+0x2a/0x48 [ 1106.400020] RSP [ 1106.400020] CR2: 0000000000000000 [ 1106.428061] ---[ end trace ae08331628ba3050 ]--- Reported-by: Jan Kara Signed-off-by: Dmitry Kasatkin Signed-off-by: Mimi Zohar Signed-off-by: Jiri Slaby

CAPABILITIES: remove undefined caps from all processes

2014-09-17T14:55:03Z

commit 7d8b6c63751cfbbe5eef81a48c22978b3407a3ad upstream. This is effectively a revert of 7b9a7ec565505699f503b4fcf61500dceb36e744 plus fixing it a different way... We found, when trying to run an application from an application which had dropped privs that the kernel does security checks on undefined capability bits. This was ESPECIALLY difficult to debug as those undefined bits are hidden from /proc/$PID/status. Consider a root application which drops all capabilities from ALL 4 capability sets. We assume, since the application is going to set eff/perm/inh from an array that it will clear not only the defined caps less than CAP_LAST_CAP, but also the higher 28ish bits which are undefined future capabilities. The BSET gets cleared differently. Instead it is cleared one bit at a time. The problem here is that in security/commoncap.c::cap_task_prctl() we actually check the validity of a capability being read. So any task which attempts to 'read all things set in bset' followed by 'unset all things set in bset' will not even attempt to unset the undefined bits higher than CAP_LAST_CAP. So the 'parent' will look something like: CapInh: 0000000000000000 CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: ffffffc000000000 All of this 'should' be fine. Given that these are undefined bits that aren't supposed to have anything to do with permissions. But they do... So lets now consider a task which cleared the eff/perm/inh completely and cleared all of the valid caps in the bset (but not the invalid caps it couldn't read out of the kernel). We know that this is exactly what the libcap-ng library does and what the go capabilities library does. They both leave you in that above situation if you try to clear all of you capapabilities from all 4 sets. If that root task calls execve() the child task will pick up all caps not blocked by the bset. The bset however does not block bits higher than CAP_LAST_CAP. So now the child task has bits in eff which are not in the parent. These are 'meaningless' undefined bits, but still bits which the parent doesn't have. The problem is now in cred_cap_issubset() (or any operation which does a subset test) as the child, while a subset for valid cap bits, is not a subset for invalid cap bits! So now we set durring commit creds that the child is not dumpable. Given it is 'more priv' than its parent. It also means the parent cannot ptrace the child and other stupidity. The solution here: 1) stop hiding capability bits in status This makes debugging easier! 2) stop giving any task undefined capability bits. it's simple, it you don't put those invalid bits in CAP_FULL_SET you won't get them in init and you won't get them in any other task either. This fixes the cap_issubset() tests and resulting fallout (which made the init task in a docker container untraceable among other things) 3) mask out undefined bits when sys_capset() is called as it might use ~0, ~0 to denote 'all capabilities' for backward/forward compatibility. This lets 'capsh --caps="all=eip" -- -c /bin/bash' run. 4) mask out undefined bit when we read a file capability off of disk as again likely all bits are set in the xattr for forward/backward compatibility. This lets 'setcap all+pe /bin/bash; /bin/bash' run Signed-off-by: Eric Paris Reviewed-by: Kees Cook Cc: Andrew Vagin Cc: Andrew G. Morgan Cc: Serge E. Hallyn Cc: Kees Cook Cc: Steve Grubb Cc: Dan Walsh Signed-off-by: James Morris Signed-off-by: Jiri Slaby

evm: prohibit userspace writing 'security.evm' HMAC value

2014-06-23T08:27:54Z

commit 2fb1c9a4f2dbc2f0bd2431c7fa64d0b5483864e4 upstream. Calculating the 'security.evm' HMAC value requires access to the EVM encrypted key. Only the kernel should have access to it. This patch prevents userspace tools(eg. setfattr, cp --preserve=xattr) from setting/modifying the 'security.evm' HMAC value directly. Signed-off-by: Mimi Zohar Signed-off-by: Jiri Slaby

ima: introduce ima_kernel_read()

2014-06-23T08:27:54Z

commit 0430e49b6e7c6b5e076be8fefdee089958c9adad upstream. Commit 8aac62706 "move exit_task_namespaces() outside of exit_notify" introduced the kernel opps since the kernel v3.10, which happens when Apparmor and IMA-appraisal are enabled at the same time. ---------------------------------------------------------------------- [ 106.750167] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 106.750221] IP: [] our_mnt+0x1a/0x30 [ 106.750241] PGD 0 [ 106.750254] Oops: 0000 [#1] SMP [ 106.750272] Modules linked in: cuse parport_pc ppdev bnep rfcomm bluetooth rpcsec_gss_krb5 nfsd auth_rpcgss nfs_acl nfs lockd sunrpc fscache dm_crypt intel_rapl x86_pkg_temp_thermal intel_powerclamp kvm_intel snd_hda_codec_hdmi kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 glue_helper lrw gf128mul ablk_helper cryptd snd_hda_codec_realtek dcdbas snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_seq_midi snd_seq_midi_event snd_rawmidi psmouse snd_seq microcode serio_raw snd_timer snd_seq_device snd soundcore video lpc_ich coretemp mac_hid lp parport mei_me mei nbd hid_generic e1000e usbhid ahci ptp hid libahci pps_core [ 106.750658] CPU: 6 PID: 1394 Comm: mysqld Not tainted 3.13.0-rc7-kds+ #15 [ 106.750673] Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A08 09/19/2012 [ 106.750689] task: ffff8800de804920 ti: ffff880400fca000 task.ti: ffff880400fca000 [ 106.750704] RIP: 0010:[] [] our_mnt+0x1a/0x30 [ 106.750725] RSP: 0018:ffff880400fcba60 EFLAGS: 00010286 [ 106.750738] RAX: 0000000000000000 RBX: 0000000000000100 RCX: ffff8800d51523e7 [ 106.750764] RDX: ffffffffffffffea RSI: ffff880400fcba34 RDI: ffff880402d20020 [ 106.750791] RBP: ffff880400fcbae0 R08: 0000000000000000 R09: 0000000000000001 [ 106.750817] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8800d5152300 [ 106.750844] R13: ffff8803eb8df510 R14: ffff880400fcbb28 R15: ffff8800d51523e7 [ 106.750871] FS: 0000000000000000(0000) GS:ffff88040d200000(0000) knlGS:0000000000000000 [ 106.750910] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 106.750935] CR2: 0000000000000018 CR3: 0000000001c0e000 CR4: 00000000001407e0 [ 106.750962] Stack: [ 106.750981] ffffffff813434eb ffff880400fcbb20 ffff880400fcbb18 0000000000000000 [ 106.751037] ffff8800de804920 ffffffff8101b9b9 0001800000000000 0000000000000100 [ 106.751093] 0000010000000000 0000000000000002 000000000000000e ffff8803eb8df500 [ 106.751149] Call Trace: [ 106.751172] [] ? aa_path_name+0x2ab/0x430 [ 106.751199] [] ? sched_clock+0x9/0x10 [ 106.751225] [] aa_path_perm+0x7d/0x170 [ 106.751250] [] ? native_sched_clock+0x15/0x80 [ 106.751276] [] aa_file_perm+0x33/0x40 [ 106.751301] [] common_file_perm+0x8e/0xb0 [ 106.751327] [] apparmor_file_permission+0x18/0x20 [ 106.751355] [] security_file_permission+0x23/0xa0 [ 106.751382] [] rw_verify_area+0x52/0xe0 [ 106.751407] [] vfs_read+0x6d/0x170 [ 106.751432] [] kernel_read+0x41/0x60 [ 106.751457] [] ima_calc_file_hash+0x225/0x280 [ 106.751483] [] ? ima_calc_file_hash+0x32/0x280 [ 106.751509] [] ima_collect_measurement+0x9d/0x160 [ 106.751536] [] ? trace_hardirqs_on+0xd/0x10 [ 106.751562] [] ? ima_file_free+0x6c/0xd0 [ 106.751587] [] ima_update_xattr+0x34/0x60 [ 106.751612] [] ima_file_free+0xc0/0xd0 [ 106.751637] [] __fput+0xd5/0x300 [ 106.751662] [] ____fput+0xe/0x10 [ 106.751687] [] task_work_run+0xc4/0xe0 [ 106.751712] [] do_exit+0x2bd/0xa90 [ 106.751738] [] ? retint_swapgs+0x13/0x1b [ 106.751763] [] do_group_exit+0x4c/0xc0 [ 106.751788] [] SyS_exit_group+0x14/0x20 [ 106.751814] [] system_call_fastpath+0x1a/0x1f [ 106.751839] Code: c3 0f 1f 44 00 00 55 48 89 e5 e8 22 fe ff ff 5d c3 0f 1f 44 00 00 55 65 48 8b 04 25 c0 c9 00 00 48 8b 80 28 06 00 00 48 89 e5 5d <48> 8b 40 18 48 39 87 c0 00 00 00 0f 94 c0 c3 0f 1f 80 00 00 00 [ 106.752185] RIP [] our_mnt+0x1a/0x30 [ 106.752214] RSP [ 106.752236] CR2: 0000000000000018 [ 106.752258] ---[ end trace 3c520748b4732721 ]--- ---------------------------------------------------------------------- The reason for the oops is that IMA-appraisal uses "kernel_read()" when file is closed. kernel_read() honors LSM security hook which calls Apparmor handler, which uses current->nsproxy->mnt_ns. The 'guilty' commit changed the order of cleanup code so that nsproxy->mnt_ns was not already available for Apparmor. Discussion about the issue with Al Viro and Eric W. Biederman suggested that kernel_read() is too high-level for IMA. Another issue, except security checking, that was identified is mandatory locking. kernel_read honors it as well and it might prevent IMA from calculating necessary hash. It was suggested to use simplified version of the function without security and locking checks. This patch introduces special version ima_kernel_read(), which skips security and mandatory locking checking. It prevents the kernel oops to happen. Signed-off-by: Dmitry Kasatkin Suggested-by: Eric W. Biederman Signed-off-by: Mimi Zohar Signed-off-by: Jiri Slaby

ima: audit log files opened with O_DIRECT flag

2014-06-20T15:34:22Z

commit f9b2a735bdddf836214b5dca74f6ca7712e5a08c upstream. Files are measured or appraised based on the IMA policy. When a file, in policy, is opened with the O_DIRECT flag, a deadlock occurs. The first attempt at resolving this lockdep temporarily removed the O_DIRECT flag and restored it, after calculating the hash. The second attempt introduced the O_DIRECT_HAVELOCK flag. Based on this flag, do_blockdev_direct_IO() would skip taking the i_mutex a second time. The third attempt, by Dmitry Kasatkin, resolves the i_mutex locking issue, by re-introducing the IMA mutex, but uncovered another problem. Reading a file with O_DIRECT flag set, writes directly to userspace pages. A second patch allocates a user-space like memory. This works for all IMA hooks, except ima_file_free(), which is called on __fput() to recalculate the file hash. Until this last issue is addressed, do not 'collect' the measurement for measuring, appraising, or auditing files opened with the O_DIRECT flag set. Based on policy, permit or deny file access. This patch defines a new IMA policy rule option named 'permit_directio'. Policy rules could be defined, based on LSM or other criteria, to permit specific applications to open files with the O_DIRECT flag set. Changelog v1: - permit or deny file access based IMA policy rules Signed-off-by: Mimi Zohar Acked-by: Dmitry Kasatkin Signed-off-by: Jiri Slaby

device_cgroup: check if exception removal is allowed

2014-06-09T13:53:24Z

commit d2c2b11cfa134f4fbdcc34088824da26a084d8de upstream. [PATCH v3 1/2] device_cgroup: check if exception removal is allowed When the device cgroup hierarchy was introduced in bd2953ebbb53 - devcg: propagate local changes down the hierarchy a specific case was overlooked. Consider the hierarchy bellow: A default policy: ALLOW, exceptions will deny access \ B default policy: ALLOW, exceptions will deny access There's no need to verify when an new exception is added to B because in this case exceptions will deny access to further devices, which is always fine. Hierarchy in device cgroup only makes sure B won't have more access than A. But when an exception is removed (by writing devices.allow), it isn't checked if the user is in fact removing an inherited exception from A, thus giving more access to B. Example: # echo 'a' >A/devices.allow # echo 'c 1:3 rw' >A/devices.deny # echo $$ >A/B/tasks # echo >/dev/null -bash: /dev/null: Operation not permitted # echo 'c 1:3 w' >A/B/devices.allow # echo >/dev/null # This shouldn't be allowed and this patch fixes it by making sure to never allow exceptions in this case to be removed if the exception is partially or fully present on the parent. v3: missing '*' in function description v2: improved log message and formatting fixes Cc: cgroups@vger.kernel.org Cc: Li Zefan Signed-off-by: Aristeu Rozanski Acked-by: Serge Hallyn Signed-off-by: Tejun Heo Signed-off-by: Jiri Slaby

device_cgroup: rework device access check and exception checking

2014-06-09T13:53:24Z

commit 79d719749d23234e9b725098aa49133f3ef7299d upstream. Whenever a device file is opened and checked against current device cgroup rules, it uses the same function (may_access()) as when a new exception rule is added by writing devices.{allow,deny}. And in both cases, the algorithm is the same, doesn't matter the behavior. First problem is having device access to be considered the same as rule checking. Consider the following structure: A (default behavior: allow, exceptions disallow access) \ B (default behavior: allow, exceptions disallow access) A new exception is added to B by writing devices.deny: c 12:34 rw When checking if that exception is allowed in may_access(): if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { if (behavior == DEVCG_DEFAULT_ALLOW) { /* the exception will deny access to certain devices */ return true; Which is ok, since B is not getting more privileges than A, it doesn't matter and the rule is accepted Now, consider it's a device file open check and the process belongs to cgroup B. The access will be generated as: behavior: allow exception: c 12:34 rw The very same chunk of code will allow it, even if there's an explicit exception telling to do otherwise. A simple test case: # mkdir new_group # cd new_group # echo $$ >tasks # echo "c 1:3 w" >devices.deny # echo >/dev/null # echo $? 0 This is a serious bug and was introduced on c39a2a3018f8 devcg: prepare may_access() for hierarchy support To solve this problem, the device file open function was split from the new exception check. Second problem is how exceptions are processed by may_access(). The first part of the said function tries to match fully with an existing exception: list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) continue; if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) continue; if (ex->major != ~0 && ex->major != refex->major) continue; if (ex->minor != ~0 && ex->minor != refex->minor) continue; if (refex->access & (~ex->access)) continue; match = true; break; } That means the new exception should be contained into an existing one to be considered a match: New exception Existing match? notes b 12:34 rwm b 12:34 rwm yes b 12:34 r b *:34 rw yes b 12:34 rw b 12:34 w no extra "r" b *:34 rw b 12:34 rw no too broad "*" b *:34 rw b *:34 rwm yes Which is fine in some cases. Consider: A (default behavior: deny, exceptions allow access) \ B (default behavior: deny, exceptions allow access) In this case the full match makes sense, the new exception cannot add more access than the parent allows But this doesn't always work, consider: A (default behavior: allow, exceptions disallow access) \ B (default behavior: deny, exceptions allow access) In this case, a new exception in B shouldn't match any of the exceptions in A, after all you can't allow something that was forbidden by A. But consider this scenario: New exception Existing in A match? outcome b 12:34 rw b 12:34 r no exception is accepted Because the new exception has "w" as extra, it doesn't match, so it'll be added to B's exception list. The same problem can happen during a file access check. Consider a cgroup with allow as default behavior: Access Exception match? b 12:34 rw b 12:34 r no In this case, the access didn't match any of the exceptions in the cgroup, which is required since exceptions will disallow access. To solve this problem, two new functions were created to match an exception either fully or partially. In the example above, a partial check will be performed and it'll produce a match since at least "b 12:34 r" from "b 12:34 rw" access matches. Cc: cgroups@vger.kernel.org Cc: Tejun Heo Cc: Serge Hallyn Cc: Li Zefan Signed-off-by: Aristeu Rozanski Signed-off-by: Tejun Heo Signed-off-by: Jiri Slaby

selinux: correctly label /proc inodes in use before the policy is loaded

2014-04-13T14:35:51Z

commit f64410ec665479d7b4b77b7519e814253ed0f686 upstream. This patch is based on an earlier patch by Eric Paris, he describes the problem below: "If an inode is accessed before policy load it will get placed on a list of inodes to be initialized after policy load. After policy load we call inode_doinit() which calls inode_doinit_with_dentry() on all inodes accessed before policy load. In the case of inodes in procfs that means we'll end up at the bottom where it does: /* Default to the fs superblock SID. */ isec->sid = sbsec->sid; if ((sbsec->flags & SE_SBPROC) && !S_ISLNK(inode->i_mode)) { if (opt_dentry) { isec->sclass = inode_mode_to_security_class(...) rc = selinux_proc_get_sid(opt_dentry, isec->sclass, &sid); if (rc) goto out_unlock; isec->sid = sid; } } Since opt_dentry is null, we'll never call selinux_proc_get_sid() and will leave the inode labeled with the label on the superblock. I believe a fix would be to mimic the behavior of xattrs. Look for an alias of the inode. If it can't be found, just leave the inode uninitialized (and pick it up later) if it can be found, we should be able to call selinux_proc_get_sid() ..." On a system exhibiting this problem, you will notice a lot of files in /proc with the generic "proc_t" type (at least the ones that were accessed early in the boot), for example: # ls -Z /proc/sys/kernel/shmmax | awk '{ print $4 " " $5 }' system_u:object_r:proc_t:s0 /proc/sys/kernel/shmmax However, with this patch in place we see the expected result: # ls -Z /proc/sys/kernel/shmmax | awk '{ print $4 " " $5 }' system_u:object_r:sysctl_kernel_t:s0 /proc/sys/kernel/shmmax Cc: Eric Paris Signed-off-by: Paul Moore Acked-by: Eric Paris Signed-off-by: Jiri Slaby

SELinux: Increase ebitmap_node size for 64-bit configuration

2014-03-12T12:25:43Z

commit a767f680e34bf14a36fefbbb6d85783eef99fd57 upstream. Currently, the ebitmap_node structure has a fixed size of 32 bytes. On a 32-bit system, the overhead is 8 bytes, leaving 24 bytes for being used as bitmaps. The overhead ratio is 1/4. On a 64-bit system, the overhead is 16 bytes. Therefore, only 16 bytes are left for bitmap purpose and the overhead ratio is 1/2. With a 3.8.2 kernel, a boot-up operation will cause the ebitmap_get_bit() function to be called about 9 million times. The average number of ebitmap_node traversal is about 3.7. This patch increases the size of the ebitmap_node structure to 64 bytes for 64-bit system to keep the overhead ratio at 1/4. This may also improve performance a little bit by making node to node traversal less frequent (< 2) as more bits are available in each node. Signed-off-by: Waiman Long Acked-by: Stephen Smalley Signed-off-by: Paul Moore Signed-off-by: Eric Paris Signed-off-by: Jiri Slaby