From 6f55d3e571a81e150bb4669c71d624dcf63813b1 Mon Sep 17 00:00:00 2001 From: Salvatore Bonaccorso Date: Thu, 12 Oct 2017 07:55:03 +0200 Subject: [PATCH] KEYS: prevent KEYCTL_READ on negative key (CVE-2017-12192) --- debian/changelog | 1 + ...-prevent-KEYCTL_READ-on-negative-key.patch | 81 +++++++++++++++++++ debian/patches/series | 1 + 3 files changed, 83 insertions(+) create mode 100644 debian/patches/bugfix/all/KEYS-prevent-KEYCTL_READ-on-negative-key.patch diff --git a/debian/changelog b/debian/changelog index f0e057fe6..b2b261c92 100644 --- a/debian/changelog +++ b/debian/changelog @@ -11,6 +11,7 @@ linux (4.13.4-2) UNRELEASED; urgency=medium * [powerpc*] Fix illegal TM state in signal handler * mac80211: fix deadlock in driver-managed RX BA session start. Thanks to Eric Côté (Closes: #878092) + * KEYS: prevent KEYCTL_READ on negative key (CVE-2017-12192) -- Ben Hutchings Wed, 04 Oct 2017 23:14:54 +0100 diff --git a/debian/patches/bugfix/all/KEYS-prevent-KEYCTL_READ-on-negative-key.patch b/debian/patches/bugfix/all/KEYS-prevent-KEYCTL_READ-on-negative-key.patch new file mode 100644 index 000000000..e34ea9bf0 --- /dev/null +++ b/debian/patches/bugfix/all/KEYS-prevent-KEYCTL_READ-on-negative-key.patch @@ -0,0 +1,81 @@ +From: Eric Biggers +Date: Mon, 18 Sep 2017 11:37:23 -0700 +Subject: KEYS: prevent KEYCTL_READ on negative key +Origin: https://git.kernel.org/linus/37863c43b2c6464f252862bf2e9768264e961678 +Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-12192 + +Because keyctl_read_key() looks up the key with no permissions +requested, it may find a negatively instantiated key. If the key is +also possessed, we went ahead and called ->read() on the key. But the +key payload will actually contain the ->reject_error rather than the +normal payload. Thus, the kernel oopses trying to read the +user_key_payload from memory address (int)-ENOKEY = 0x00000000ffffff82. + +Fortunately the payload data is stored inline, so it shouldn't be +possible to abuse this as an arbitrary memory read primitive... + +Reproducer: + keyctl new_session + keyctl request2 user desc '' @s + keyctl read $(keyctl show | awk '/user: desc/ {print $1}') + +It causes a crash like the following: + BUG: unable to handle kernel paging request at 00000000ffffff92 + IP: user_read+0x33/0xa0 + PGD 36a54067 P4D 36a54067 PUD 0 + Oops: 0000 [#1] SMP + CPU: 0 PID: 211 Comm: keyctl Not tainted 4.14.0-rc1 #337 + Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014 + task: ffff90aa3b74c3c0 task.stack: ffff9878c0478000 + RIP: 0010:user_read+0x33/0xa0 + RSP: 0018:ffff9878c047bee8 EFLAGS: 00010246 + RAX: 0000000000000001 RBX: ffff90aa3d7da340 RCX: 0000000000000017 + RDX: 0000000000000000 RSI: 00000000ffffff82 RDI: ffff90aa3d7da340 + RBP: ffff9878c047bf00 R08: 00000024f95da94f R09: 0000000000000000 + R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 + R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 + FS: 00007f58ece69740(0000) GS:ffff90aa3e200000(0000) knlGS:0000000000000000 + CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 + CR2: 00000000ffffff92 CR3: 0000000036adc001 CR4: 00000000003606f0 + Call Trace: + keyctl_read_key+0xac/0xe0 + SyS_keyctl+0x99/0x120 + entry_SYSCALL_64_fastpath+0x1f/0xbe + RIP: 0033:0x7f58ec787bb9 + RSP: 002b:00007ffc8d401678 EFLAGS: 00000206 ORIG_RAX: 00000000000000fa + RAX: ffffffffffffffda RBX: 00007ffc8d402800 RCX: 00007f58ec787bb9 + RDX: 0000000000000000 RSI: 00000000174a63ac RDI: 000000000000000b + RBP: 0000000000000004 R08: 00007ffc8d402809 R09: 0000000000000020 + R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffc8d402800 + R13: 00007ffc8d4016e0 R14: 0000000000000000 R15: 0000000000000000 + Code: e5 41 55 49 89 f5 41 54 49 89 d4 53 48 89 fb e8 a4 b4 ad ff 85 c0 74 09 80 3d b9 4c 96 00 00 74 43 48 8b b3 20 01 00 00 4d 85 ed <0f> b7 5e 10 74 29 4d 85 e4 74 24 4c 39 e3 4c 89 e2 4c 89 ef 48 + RIP: user_read+0x33/0xa0 RSP: ffff9878c047bee8 + CR2: 00000000ffffff92 + +Fixes: 61ea0c0ba904 ("KEYS: Skip key state checks when checking for possession") +Cc: [v3.13+] +Signed-off-by: Eric Biggers +Signed-off-by: David Howells +--- + security/keys/keyctl.c | 5 +++++ + 1 file changed, 5 insertions(+) + +diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c +index aa1d11a29136..365ff85d7e27 100644 +--- a/security/keys/keyctl.c ++++ b/security/keys/keyctl.c +@@ -766,6 +766,11 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) + + key = key_ref_to_ptr(key_ref); + ++ if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) { ++ ret = -ENOKEY; ++ goto error2; ++ } ++ + /* see if we can read it directly */ + ret = key_permission(key_ref, KEY_NEED_READ); + if (ret == 0) +-- +2.15.0.rc0 + diff --git a/debian/patches/series b/debian/patches/series index 01ec97378..82a5b45c7 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -123,6 +123,7 @@ bugfix/all/fix-infoleak-in-waitid-2.patch bugfix/all/brcmfmac-add-length-check-in-brcmf_cfg80211_escan_ha.patch bugfix/all/powerpc-64s-Use-emergency-stack-for-kernel-TM-Bad-Th.patch bugfix/all/powerpc-tm-Fix-illegal-TM-state-in-signal-handler.patch +bugfix/all/KEYS-prevent-KEYCTL_READ-on-negative-key.patch # Fix exported symbol versions bugfix/alpha/alpha-restore-symbol-versions-for-symbols-exported-f.patch