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  1. 30 Dec, 2015 32 commits
  3. 27 Nov, 2015 8 commits
    • Ben Hutchings's avatar
      Linux 3.2.74 · 95afdc9f
      Ben Hutchings authored
      95afdc9f
    • Christophe Leroy's avatar
      splice: sendfile() at once fails for big files · fcb27817
      Christophe Leroy authored 
      commit 0ff28d9f upstream.

Using sendfile with below small program to get MD5 sums of some files,
it appear that big files (over 64kbytes with 4k pages system) get a
wrong MD5 sum while small files get the correct sum.
This program uses sendfile() to send a file to an AF_ALG socket
for hashing.

/* md5sum2.c */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <linux/if_alg.h>

int main(int argc, char **argv)
{
	int sk = socket(AF_ALG, SOCK_SEQPACKET, 0);
	struct stat st;
	struct sockaddr_alg sa = {
		.salg_family = AF_ALG,
		.salg_type = "hash",
		.salg_name = "md5",
	};
	int n;

	bind(sk, (struct sockaddr*)&sa, sizeof(sa));

	for (n = 1; n < argc; n++) {
		int size;
		int offset = 0;
		char buf[4096];
		int fd;
		int sko;
		int i;

		fd = open(argv[n], O_RDONLY);
		sko = accept(sk, NULL, 0);
		fstat(fd, &st);
		size = st.st_size;
		sendfile(sko, fd, &offset, size);
		size = read(sko, buf, sizeof(buf));
		for (i = 0; i < size; i++)
			printf("%2.2x", buf[i]);
		printf("  %s\n", argv[n]);
		close(fd);
		close(sko);
	}
	exit(0);
}

Test below is done using official linux patch files. First result is
with a software based md5sum. Second result is with the program above.

root@vgoip:~# ls -l patch-3.6.*
-rw-r--r--    1 root     root         64011 Aug 24 12:01 patch-3.6.2.gz
-rw-r--r--    1 root     root         94131 Aug 24 12:01 patch-3.6.3.gz

root@vgoip:~# md5sum patch-3.6.*
b3ffb9848196846f31b2ff133d2d6443  patch-3.6.2.gz
c5e8f687878457db77cb7158c38a7e43  patch-3.6.3.gz

root@vgoip:~# ./md5sum2 patch-3.6.*
b3ffb9848196846f31b2ff133d2d6443  patch-3.6.2.gz
5fd77b24e68bb24dcc72d6e57c64790e  patch-3.6.3.gz

After investivation, it appears that sendfile() sends the files by blocks
of 64kbytes (16 times PAGE_SIZE). The problem is that at the end of each
block, the SPLICE_F_MORE flag is missing, therefore the hashing operation
is reset as if it was the end of the file.

This patch adds SPLICE_F_MORE to the flags when more data is pending.

With the patch applied, we get the correct sums:

root@vgoip:~# md5sum patch-3.6.*
b3ffb9848196846f31b2ff133d2d6443  patch-3.6.2.gz
c5e8f687878457db77cb7158c38a7e43  patch-3.6.3.gz

root@vgoip:~# ./md5sum2 patch-3.6.*
b3ffb9848196846f31b2ff133d2d6443  patch-3.6.2.gz
c5e8f687878457db77cb7158c38a7e43  patch-3.6.3.gz
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      fcb27817
    • Eric Dumazet's avatar
      net: avoid NULL deref in inet_ctl_sock_destroy() · f79c83d6
      Eric Dumazet authored 
      [ Upstream commit 8fa677d2 ]

Under low memory conditions, tcp_sk_init() and icmp_sk_init()
can both iterate on all possible cpus and call inet_ctl_sock_destroy(),
with eventual NULL pointer.
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      f79c83d6
    • Ani Sinha's avatar
      ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context. · 33cf84ba
      Ani Sinha authored 
      [ Upstream commit 44f49dd8 ]

Fixes the following kernel BUG :

BUG: using __this_cpu_add() in preemptible [00000000] code: bash/2758
caller is __this_cpu_preempt_check+0x13/0x15
CPU: 0 PID: 2758 Comm: bash Tainted: P           O   3.18.19 #2
 ffffffff8170eaca ffff880110d1b788 ffffffff81482b2a 0000000000000000
 0000000000000000 ffff880110d1b7b8 ffffffff812010ae ffff880007cab800
 ffff88001a060800 ffff88013a899108 ffff880108b84240 ffff880110d1b7c8
Call Trace:
[<ffffffff81482b2a>] dump_stack+0x52/0x80
[<ffffffff812010ae>] check_preemption_disabled+0xce/0xe1
[<ffffffff812010d4>] __this_cpu_preempt_check+0x13/0x15
[<ffffffff81419d60>] ipmr_queue_xmit+0x647/0x70c
[<ffffffff8141a154>] ip_mr_forward+0x32f/0x34e
[<ffffffff8141af76>] ip_mroute_setsockopt+0xe03/0x108c
[<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
[<ffffffff810e6974>] ? pollwake+0x4d/0x51
[<ffffffff81058ac0>] ? default_wake_function+0x0/0xf
[<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
[<ffffffff810613d9>] ? __wake_up_common+0x45/0x77
[<ffffffff81486ea9>] ? _raw_spin_unlock_irqrestore+0x1d/0x32
[<ffffffff810618bc>] ? __wake_up_sync_key+0x4a/0x53
[<ffffffff8139a519>] ? sock_def_readable+0x71/0x75
[<ffffffff813dd226>] do_ip_setsockopt+0x9d/0xb55
[<ffffffff81429818>] ? unix_seqpacket_sendmsg+0x3f/0x41
[<ffffffff813963fe>] ? sock_sendmsg+0x6d/0x86
[<ffffffff813959d4>] ? sockfd_lookup_light+0x12/0x5d
[<ffffffff8139650a>] ? SyS_sendto+0xf3/0x11b
[<ffffffff810d5738>] ? new_sync_read+0x82/0xaa
[<ffffffff813ddd19>] compat_ip_setsockopt+0x3b/0x99
[<ffffffff813fb24a>] compat_raw_setsockopt+0x11/0x32
[<ffffffff81399052>] compat_sock_common_setsockopt+0x18/0x1f
[<ffffffff813c4d05>] compat_SyS_setsockopt+0x1a9/0x1cf
[<ffffffff813c4149>] compat_SyS_socketcall+0x180/0x1e3
[<ffffffff81488ea1>] cstar_dispatch+0x7/0x1e
Signed-off-by: default avatarAni Sinha <ani@arista.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: ipmr doesn't implement IPSTATS_MIB_OUTOCTETS]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      33cf84ba
    • Sowmini Varadhan's avatar
      RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data_recv · f114d937
      Sowmini Varadhan authored 
      [ Upstream commit 8ce675ff ]

Either of pskb_pull() or pskb_trim() may fail under low memory conditions.
If rds_tcp_data_recv() ignores such failures, the application will
receive corrupted data because the skb has not been correctly
carved to the RDS datagram size.

Avoid this by handling pskb_pull/pskb_trim failure in the same
manner as the skb_clone failure: bail out of rds_tcp_data_recv(), and
retry via the deferred call to rds_send_worker() that gets set up on
ENOMEM from rds_tcp_read_sock()
Signed-off-by: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: default avatarSantosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      f114d937
    • Dan Carpenter's avatar
      irda: precedence bug in irlmp_seq_hb_idx() · a8ab3e63
      Dan Carpenter authored 
      [ Upstream commit 50010c20 ]

This is decrementing the pointer, instead of the value stored in the
pointer.  KASan detects it as an out of bounds reference.
Reported-by: default avatar"Berry Cheng 程君(成淼)" <chengmiao.cj@alibaba-inc.com>
Signed-off-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      a8ab3e63
    • Jann Horn's avatar
      fs: if a coredump already exists, unlink and recreate with O_EXCL · b208d27d
      Jann Horn authored 
      commit fbb18169 upstream.

It was possible for an attacking user to trick root (or another user) into
writing his coredumps into an attacker-readable, pre-existing file using
rename() or link(), causing the disclosure of secret data from the victim
process' virtual memory.  Depending on the configuration, it was also
possible to trick root into overwriting system files with coredumps.  Fix
that issue by never writing coredumps into existing files.

Requirements for the attack:
 - The attack only applies if the victim's process has a nonzero
   RLIMIT_CORE and is dumpable.
 - The attacker can trick the victim into coredumping into an
   attacker-writable directory D, either because the core_pattern is
   relative and the victim's cwd is attacker-writable or because an
   absolute core_pattern pointing to a world-writable directory is used.
 - The attacker has one of these:
  A: on a system with protected_hardlinks=0:
     execute access to a folder containing a victim-owned,
     attacker-readable file on the same partition as D, and the
     victim-owned file will be deleted before the main part of the attack
     takes place. (In practice, there are lots of files that fulfill
     this condition, e.g. entries in Debian's /var/lib/dpkg/info/.)
     This does not apply to most Linux systems because most distros set
     protected_hardlinks=1.
  B: on a system with protected_hardlinks=1:
     execute access to a folder containing a victim-owned,
     attacker-readable and attacker-writable file on the same partition
     as D, and the victim-owned file will be deleted before the main part
     of the attack takes place.
     (This seems to be uncommon.)
  C: on any system, independent of protected_hardlinks:
     write access to a non-sticky folder containing a victim-owned,
     attacker-readable file on the same partition as D
     (This seems to be uncommon.)

The basic idea is that the attacker moves the victim-owned file to where
he expects the victim process to dump its core.  The victim process dumps
its core into the existing file, and the attacker reads the coredump from
it.

If the attacker can't move the file because he does not have write access
to the containing directory, he can instead link the file to a directory
he controls, then wait for the original link to the file to be deleted
(because the kernel checks that the link count of the corefile is 1).

A less reliable variant that requires D to be non-sticky works with link()
and does not require deletion of the original link: link() the file into
D, but then unlink() it directly before the kernel performs the link count
check.

On systems with protected_hardlinks=0, this variant allows an attacker to
not only gain information from coredumps, but also clobber existing,
victim-writable files with coredumps.  (This could theoretically lead to a
privilege escalation.)
Signed-off-by: default avatarJann Horn <jann@thejh.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      b208d27d
    • Kees Cook's avatar
      fs: make dumpable=2 require fully qualified path · 0677d4e0
      Kees Cook authored 
      commit 9520628e upstream.

When the suid_dumpable sysctl is set to "2", and there is no core dump
pipe defined in the core_pattern sysctl, a local user can cause core files
to be written to root-writable directories, potentially with
user-controlled content.

This means an admin can unknowningly reintroduce a variation of
CVE-2006-2451, allowing local users to gain root privileges.

  $ cat /proc/sys/fs/suid_dumpable
  2
  $ cat /proc/sys/kernel/core_pattern
  core
  $ ulimit -c unlimited
  $ cd /
  $ ls -l core
  ls: cannot access core: No such file or directory
  $ touch core
  touch: cannot touch `core': Permission denied
  $ OHAI="evil-string-here" ping localhost >/dev/null 2>&1 &
  $ pid=$!
  $ sleep 1
  $ kill -SEGV $pid
  $ ls -l core
  -rw------- 1 root kees 458752 Jun 21 11:35 core
  $ sudo strings core | grep evil
  OHAI=evil-string-here

While cron has been fixed to abort reading a file when there is any
parse error, there are still other sensitive directories that will read
any file present and skip unparsable lines.

Instead of introducing a suid_dumpable=3 mode and breaking all users of
mode 2, this only disables the unsafe portion of mode 2 (writing to disk
via relative path).  Most users of mode 2 (e.g.  Chrome OS) already use
a core dump pipe handler, so this change will not break them.  For the
situations where a pipe handler is not defined but mode 2 is still
active, crash dumps will only be written to fully qualified paths.  If a
relative path is defined (e.g.  the default "core" pattern), dump
attempts will trigger a printk yelling about the lack of a fully
qualified path.
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alan Cox <alan@linux.intel.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Reviewed-by: default avatarJames Morris <james.l.morris@oracle.com>
      0677d4e0
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