[linux] 01/02: KEYS: potential uninitialized variable (CVE-2016-4470)
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Fri Jun 24 21:51:48 UTC 2016
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benh pushed a commit to branch jessie-security
in repository linux.
commit d7574c1564b1eef2270ce5da2969105d61572bd5
Author: Ben Hutchings <ben at decadent.org.uk>
Date: Fri Jun 24 22:06:14 2016 +0200
KEYS: potential uninitialized variable (CVE-2016-4470)
---
debian/changelog | 1 +
.../keys-potential-uninitialized-variable.patch | 86 ++++++++++++++++++++++
debian/patches/series | 1 +
3 files changed, 88 insertions(+)
diff --git a/debian/changelog b/debian/changelog
index 688d827..f4b7b18 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -41,6 +41,7 @@ linux (3.16.7-ckt25-2+deb8u1) UNRELEASED; urgency=medium
* net: fix a kernel infoleak in x25 module (CVE-2016-4580)
* IB/security: Restrict use of the write() interface (CVE-2016-4565)
* ppp: take reference on channels netns (CVE-2016-4805)
+ * KEYS: potential uninitialized variable (CVE-2016-4470)
[ Salvatore Bonaccorso ]
* [x86] USB: usbip: fix potential out-of-bounds write (CVE-2016-3955)
diff --git a/debian/patches/bugfix/all/keys-potential-uninitialized-variable.patch b/debian/patches/bugfix/all/keys-potential-uninitialized-variable.patch
new file mode 100644
index 0000000..e58c076
--- /dev/null
+++ b/debian/patches/bugfix/all/keys-potential-uninitialized-variable.patch
@@ -0,0 +1,86 @@
+From: Dan Carpenter <dan.carpenter at oracle.com>
+Date: Thu, 16 Jun 2016 15:48:57 +0100
+Subject: KEYS: potential uninitialized variable
+Origin: https://git.kernel.org/linus/38327424b40bcebe2de92d07312c89360ac9229a
+
+If __key_link_begin() failed then "edit" would be uninitialized. I've
+added a check to fix that.
+
+This allows a random user to crash the kernel, though it's quite
+difficult to achieve. There are three ways it can be done as the user
+would have to cause an error to occur in __key_link():
+
+ (1) Cause the kernel to run out of memory. In practice, this is difficult
+ to achieve without ENOMEM cropping up elsewhere and aborting the
+ attempt.
+
+ (2) Revoke the destination keyring between the keyring ID being looked up
+ and it being tested for revocation. In practice, this is difficult to
+ time correctly because the KEYCTL_REJECT function can only be used
+ from the request-key upcall process. Further, users can only make use
+ of what's in /sbin/request-key.conf, though this does including a
+ rejection debugging test - which means that the destination keyring
+ has to be the caller's session keyring in practice.
+
+ (3) Have just enough key quota available to create a key, a new session
+ keyring for the upcall and a link in the session keyring, but not then
+ sufficient quota to create a link in the nominated destination keyring
+ so that it fails with EDQUOT.
+
+The bug can be triggered using option (3) above using something like the
+following:
+
+ echo 80 >/proc/sys/kernel/keys/root_maxbytes
+ keyctl request2 user debug:fred negate @t
+
+The above sets the quota to something much lower (80) to make the bug
+easier to trigger, but this is dependent on the system. Note also that
+the name of the keyring created contains a random number that may be
+between 1 and 10 characters in size, so may throw the test off by
+changing the amount of quota used.
+
+Assuming the failure occurs, something like the following will be seen:
+
+ kfree_debugcheck: out of range ptr 6b6b6b6b6b6b6b68h
+ ------------[ cut here ]------------
+ kernel BUG at ../mm/slab.c:2821!
+ ...
+ RIP: 0010:[<ffffffff811600f9>] kfree_debugcheck+0x20/0x25
+ RSP: 0018:ffff8804014a7de8 EFLAGS: 00010092
+ RAX: 0000000000000034 RBX: 6b6b6b6b6b6b6b68 RCX: 0000000000000000
+ RDX: 0000000000040001 RSI: 00000000000000f6 RDI: 0000000000000300
+ RBP: ffff8804014a7df0 R08: 0000000000000001 R09: 0000000000000000
+ R10: ffff8804014a7e68 R11: 0000000000000054 R12: 0000000000000202
+ R13: ffffffff81318a66 R14: 0000000000000000 R15: 0000000000000001
+ ...
+ Call Trace:
+ kfree+0xde/0x1bc
+ assoc_array_cancel_edit+0x1f/0x36
+ __key_link_end+0x55/0x63
+ key_reject_and_link+0x124/0x155
+ keyctl_reject_key+0xb6/0xe0
+ keyctl_negate_key+0x10/0x12
+ SyS_keyctl+0x9f/0xe7
+ do_syscall_64+0x63/0x13a
+ entry_SYSCALL64_slow_path+0x25/0x25
+
+Fixes: f70e2e06196a ('KEYS: Do preallocation for __key_link()')
+Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
+Signed-off-by: David Howells <dhowells at redhat.com>
+cc: stable at vger.kernel.org
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+---
+ security/keys/key.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/security/keys/key.c
++++ b/security/keys/key.c
+@@ -575,7 +575,7 @@ int key_reject_and_link(struct key *key,
+
+ mutex_unlock(&key_construction_mutex);
+
+- if (keyring)
++ if (keyring && link_ret == 0)
+ __key_link_end(keyring, &key->index_key, edit);
+
+ /* wake up anyone waiting for a key to be constructed */
diff --git a/debian/patches/series b/debian/patches/series
index 9766e20..d64a5fa 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -702,3 +702,4 @@ bugfix/all/net-fix-infoleak-in-rtnetlink.patch
bugfix/all/net-fix-a-kernel-infoleak-in-x25-module.patch
bugfix/all/ib-security-restrict-use-of-the-write-interface.patch
bugfix/all/ppp-take-reference-on-channels-netns.patch
+bugfix/all/keys-potential-uninitialized-variable.patch
--
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