db-d2/primevul-codebert-embeddings huggingface dataset:
Commit message: userns:  Don't allow creation if the user is chrooted

Guarantee that the policy of which files may be access that is
established by setting the root directory will not be violated
by user namespaces by verifying that the root directory points
to the root of the mount namespace at the time of user namespace
creation.

Changing the root is a privileged operation, and as a matter of policy
it serves to limit unprivileged processes to files below the current
root directory.

For reasons of simplicity and comprehensibility the privilege to
change the root directory is gated solely on the CAP_SYS_CHROOT
capability in the user namespace.  Therefore when creating a user
namespace we must ensure that the policy of which files may be access
can not be violated by changing the root directory.

Anyone who runs a processes in a chroot and would like to use user
namespace can setup the same view of filesystems with a mount
namespace instead.  With this result that this is not a practical
limitation for using user namespaces.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
CVE: CVE-2013-1956
CWE: CWE-264
Vulnerability description: The create_user_ns function in kernel/user_namespace.c in the Linux kernel before 3.8.6 does not check whether a chroot directory exists that differs from the namespace root directory, which allows local users to bypass intended filesystem restrictions via a crafted clone system call.

Project: linux
File: user_namespace.c

int create_user_ns(struct cred *new)
{
	struct user_namespace *ns, *parent_ns = new->user_ns;
	kuid_t owner = new->euid;
 	kgid_t group = new->egid;
 	int ret;
 
	/*
	 * Verify that we can not violate the policy of which files
	 * may be accessed that is specified by the root directory,
	 * by verifing that the root directory is at the root of the
	 * mount namespace which allows all files to be accessed.
	 */
	if (current_chrooted())
		return -EPERM;

 	/* The creator needs a mapping in the parent user namespace
 	 * or else we won't be able to reasonably tell userspace who
 	 * created a user_namespace.
	 */
	if (!kuid_has_mapping(parent_ns, owner) ||
	    !kgid_has_mapping(parent_ns, group))
		return -EPERM;

	ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
	if (!ns)
		return -ENOMEM;

	ret = proc_alloc_inum(&ns->proc_inum);
	if (ret) {
		kmem_cache_free(user_ns_cachep, ns);
		return ret;
	}

	atomic_set(&ns->count, 1);
	/* Leave the new->user_ns reference with the new user namespace. */
	ns->parent = parent_ns;
	ns->owner = owner;
	ns->group = group;

	set_cred_user_ns(new, ns);

	return 0;
}
Commit message: cookie: fix tailmatching to prevent cross-domain leakage

Cookies set for 'example.com' could accidentaly also be sent by libcurl
to the 'bexample.com' (ie with a prefix to the first domain name).

This is a security vulnerabilty, CVE-2013-1944.

Bug: http://curl.haxx.se/docs/adv_20130412.html
CVE: CVE-2013-1944
CWE: CWE-200
Vulnerability description: The tailMatch function in cookie.c in cURL and libcurl before 7.30.0 does not properly match the path domain when sending cookies, which allows remote attackers to steal cookies via a matching suffix in the domain of a URL.

Project: curl

static bool tailmatch(const char *little, const char *bigone)
static bool tailmatch(const char *cooke_domain, const char *hostname)
 {
  size_t cookie_domain_len = strlen(cooke_domain);
  size_t hostname_len = strlen(hostname);
 
  if(hostname_len < cookie_domain_len)
     return FALSE;
 
  if(!Curl_raw_equal(cooke_domain, hostname+hostname_len-cookie_domain_len))
    return FALSE;

  /* A lead char of cookie_domain is not '.'.
     RFC6265 4.1.2.3. The Domain Attribute says:
       For example, if the value of the Domain attribute is
       "example.com", the user agent will include the cookie in the Cookie
       header when making HTTP requests to example.com, www.example.com, and
       www.corp.example.com.
   */
  if(hostname_len == cookie_domain_len)
    return TRUE;
  if('.' == *(hostname + hostname_len - cookie_domain_len - 1))
    return TRUE;
  return FALSE;
 }
Commit message: fs/compat_ioctl.c: VIDEO_SET_SPU_PALETTE missing error check

The compat ioctl for VIDEO_SET_SPU_PALETTE was missing an error check
while converting ioctl arguments.  This could lead to leaking kernel
stack contents into userspace.

Patch extracted from existing fix in grsecurity.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: David Miller <davem@davemloft.net>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: PaX Team <pageexec@freemail.hu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2013-1928
CWE: CWE-200
Vulnerability description: The do_video_set_spu_palette function in fs/compat_ioctl.c in the Linux kernel before 3.6.5 on unspecified architectures lacks a certain error check, which might allow local users to obtain sensitive information from kernel stack memory via a crafted VIDEO_SET_SPU_PALETTE ioctl call on a /dev/dvb device.

Project: linux
File: compat_ioctl.c

static int do_video_set_spu_palette(unsigned int fd, unsigned int cmd,
		struct compat_video_spu_palette __user *up)
{
	struct video_spu_palette __user *up_native;
	compat_uptr_t palp;
	int length, err;
 
 	err  = get_user(palp, &up->palette);
 	err |= get_user(length, &up->length);
	if (err)
		return -EFAULT;
 
 	up_native = compat_alloc_user_space(sizeof(struct video_spu_palette));
 	err  = put_user(compat_ptr(palp), &up_native->palette);
	err |= put_user(length, &up_native->length);
	if (err)
		return -EFAULT;

	err = sys_ioctl(fd, cmd, (unsigned long) up_native);

	return err;
}
Commit message: net/sctp: Validate parameter size for SCTP_GET_ASSOC_STATS

Building sctp may fail with:

In function ‘copy_from_user’,
    inlined from ‘sctp_getsockopt_assoc_stats’ at
    net/sctp/socket.c:5656:20:
arch/x86/include/asm/uaccess_32.h:211:26: error: call to
    ‘copy_from_user_overflow’ declared with attribute error: copy_from_user()
    buffer size is not provably correct

if built with W=1 due to a missing parameter size validation
before the call to copy_from_user.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2013-1828
CWE: CWE-20
Vulnerability description: The sctp_getsockopt_assoc_stats function in net/sctp/socket.c in the Linux kernel before 3.8.4 does not validate a size value before proceeding to a copy_from_user operation, which allows local users to gain privileges via a crafted application that contains an SCTP_GET_ASSOC_STATS getsockopt system call.

Project: linux

static int sctp_getsockopt_assoc_stats(struct sock *sk, int len,
				       char __user *optval,
				       int __user *optlen)
{
	struct sctp_assoc_stats sas;
	struct sctp_association *asoc = NULL;

	/* User must provide at least the assoc id */
 	if (len < sizeof(sctp_assoc_t))
 		return -EINVAL;
 
	/* Allow the struct to grow and fill in as much as possible */
	len = min_t(size_t, len, sizeof(sas));

 	if (copy_from_user(&sas, optval, len))
 		return -EFAULT;
 
	asoc = sctp_id2assoc(sk, sas.sas_assoc_id);
	if (!asoc)
		return -EINVAL;

	sas.sas_rtxchunks = asoc->stats.rtxchunks;
	sas.sas_gapcnt = asoc->stats.gapcnt;
	sas.sas_outofseqtsns = asoc->stats.outofseqtsns;
	sas.sas_osacks = asoc->stats.osacks;
	sas.sas_isacks = asoc->stats.isacks;
	sas.sas_octrlchunks = asoc->stats.octrlchunks;
	sas.sas_ictrlchunks = asoc->stats.ictrlchunks;
	sas.sas_oodchunks = asoc->stats.oodchunks;
	sas.sas_iodchunks = asoc->stats.iodchunks;
	sas.sas_ouodchunks = asoc->stats.ouodchunks;
	sas.sas_iuodchunks = asoc->stats.iuodchunks;
	sas.sas_idupchunks = asoc->stats.idupchunks;
	sas.sas_opackets = asoc->stats.opackets;
	sas.sas_ipackets = asoc->stats.ipackets;

	/* New high max rto observed, will return 0 if not a single
	 * RTO update took place. obs_rto_ipaddr will be bogus
	 * in such a case
	 */
	sas.sas_maxrto = asoc->stats.max_obs_rto;
	memcpy(&sas.sas_obs_rto_ipaddr, &asoc->stats.obs_rto_ipaddr,
		sizeof(struct sockaddr_storage));

 	/* Mark beginning of a new observation period */
 	asoc->stats.max_obs_rto = asoc->rto_min;
 
 	if (put_user(len, optlen))
 		return -EFAULT;
 
	SCTP_DEBUG_PRINTK("sctp_getsockopt_assoc_stat(%d): %d\n",
			  len, sas.sas_assoc_id);

	if (copy_to_user(optval, &sas, len))
		return -EFAULT;

	return 0;
}
Commit message: None
CVE: CVE-2013-1772
CWE: CWE-119
Vulnerability description: The log_prefix function in kernel/printk.c in the Linux kernel 3.x before 3.4.33 does not properly remove a prefix string from a syslog header, which allows local users to cause a denial of service (buffer overflow and system crash) by leveraging /dev/kmsg write access and triggering a call_console_drivers function call.

Project: linux

static void call_console_drivers(unsigned start, unsigned end)
{
	unsigned cur_index, start_print;
	static int msg_level = -1;

	BUG_ON(((int)(start - end)) > 0);

	cur_index = start;
 	start_print = start;
 	while (cur_index != end) {
 		if (msg_level < 0 && ((end - cur_index) > 2)) {
			/*
			 * prepare buf_prefix, as a contiguous array,
			 * to be processed by log_prefix function
			 */
			char buf_prefix[SYSLOG_PRI_MAX_LENGTH+1];
			unsigned i;
			for (i = 0; i < ((end - cur_index)) && (i < SYSLOG_PRI_MAX_LENGTH); i++) {
				buf_prefix[i] = LOG_BUF(cur_index + i);
			}
			buf_prefix[i] = '\0'; /* force '\0' as last string character */

 			/* strip log prefix */
			cur_index += log_prefix((const char *)&buf_prefix, &msg_level, NULL);
 			start_print = cur_index;
 		}
 		while (cur_index != end) {
			char c = LOG_BUF(cur_index);

			cur_index++;
			if (c == '\n') {
				if (msg_level < 0) {
					/*
					 * printk() has already given us loglevel tags in
					 * the buffer.  This code is here in case the
					 * log buffer has wrapped right round and scribbled
					 * on those tags
					 */
					msg_level = default_message_loglevel;
				}
				_call_console_drivers(start_print, cur_index, msg_level);
				msg_level = -1;
				start_print = cur_index;
				break;
			}
		}
	}
	_call_console_drivers(start_print, end, msg_level);
}
Commit message: Drop packets forwarded via TCP if they are too big (CVE-2013-1428).

Normally all requests sent via the meta connections are checked so that they
cannot be larger than the input buffer. However, when packets are forwarded via
meta connections, they are copied into a packet buffer without checking whether
it fits into it. Since the packet buffer is allocated on the stack, this in
effect allows an authenticated remote node to cause a stack overflow.

This issue was found by Martin Schobert.
CVE: CVE-2013-1428
CWE: CWE-119
Vulnerability description: Stack-based buffer overflow in the receive_tcppacket function in net_packet.c in tinc before 1.0.21 and 1.1 before 1.1pre7 allows remote authenticated peers to cause a denial of service (crash) or possibly execute arbitrary code via a large TCP packet.

Project: tinc
File: net_packet.c

 void receive_tcppacket(connection_t *c, const char *buffer, int len) {
 	vpn_packet_t outpkt;
 
	if(len > sizeof outpkt.data)
		return;

 	outpkt.len = len;
 	if(c->options & OPTION_TCPONLY)
 		outpkt.priority = 0;
	else
		outpkt.priority = -1;
	memcpy(outpkt.data, buffer, len);

	receive_packet(c->node, &outpkt);
}
Commit message: PKINIT null pointer deref [CVE-2013-1415]

Don't dereference a null pointer when cleaning up.

The KDC plugin for PKINIT can dereference a null pointer when a
malformed packet causes processing to terminate early, leading to
a crash of the KDC process.  An attacker would need to have a valid
PKINIT certificate or have observed a successful PKINIT authentication,
or an unauthenticated attacker could execute the attack if anonymous
PKINIT is enabled.

CVSSv2 vector: AV:N/AC:M/Au:N/C:N/I:N/A:C/E:P/RL:O/RC:C

This is a minimal commit for pullup; style fixes in a followup.
[kaduk@mit.edu: reformat and edit commit message]

(cherry picked from commit c773d3c775e9b2d88bcdff5f8a8ba88d7ec4e8ed)

ticket: 7570
version_fixed: 1.11.1
status: resolved
CVE: CVE-2013-1415
CWE: CWE-476
Vulnerability description: The pkinit_check_kdc_pkid function in plugins/preauth/pkinit/pkinit_crypto_openssl.c in the PKINIT implementation in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.10.4 and 1.11.x before 1.11.1 does not properly handle errors during extraction of fields from an X.509 certificate, which allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a malformed KRB5_PADATA_PK_AS_REQ AS-REQ request.

Project: krb5

pkinit_check_kdc_pkid(krb5_context context,
                      pkinit_plg_crypto_context plg_cryptoctx,
                      pkinit_req_crypto_context req_cryptoctx,
                      pkinit_identity_crypto_context id_cryptoctx,
                      unsigned char *pdid_buf,
                      unsigned int pkid_len,
                      int *valid_kdcPkId)
{
    krb5_error_code retval = KRB5KDC_ERR_PREAUTH_FAILED;
    PKCS7_ISSUER_AND_SERIAL *is = NULL;
    const unsigned char *p = pdid_buf;
    int status = 1;
    X509 *kdc_cert = sk_X509_value(id_cryptoctx->my_certs, id_cryptoctx->cert_index);

    *valid_kdcPkId = 0;
     pkiDebug("found kdcPkId in AS REQ\n");
     is = d2i_PKCS7_ISSUER_AND_SERIAL(NULL, &p, (int)pkid_len);
     if (is == NULL)
        return retval;
 
     status = X509_NAME_cmp(X509_get_issuer_name(kdc_cert), is->issuer);
     if (!status) {
        status = ASN1_INTEGER_cmp(X509_get_serialNumber(kdc_cert), is->serial);
        if (!status)
            *valid_kdcPkId = 1;
     }
 
     retval = 0;
     X509_NAME_free(is->issuer);
     ASN1_INTEGER_free(is->serial);
     free(is);

    return retval;
}
Commit message: signal: always clear sa_restorer on execve

When the new signal handlers are set up, the location of sa_restorer is
not cleared, leaking a parent process's address space location to
children.  This allows for a potential bypass of the parent's ASLR by
examining the sa_restorer value returned when calling sigaction().

Based on what should be considered "secret" about addresses, it only
matters across the exec not the fork (since the VMAs haven't changed
until the exec).  But since exec sets SIG_DFL and keeps sa_restorer,
this is where it should be fixed.

Given the few uses of sa_restorer, a "set" function was not written
since this would be the only use.  Instead, we use
__ARCH_HAS_SA_RESTORER, as already done in other places.

Example of the leak before applying this patch:

  $ cat /proc/$$/maps
  ...
  7fb9f3083000-7fb9f3238000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
  ...
  $ ./leak
  ...
  7f278bc74000-7f278be29000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
  ...
  1 0 (nil) 0x7fb9f30b94a0
  2 4000000 (nil) 0x7f278bcaa4a0
  3 4000000 (nil) 0x7f278bcaa4a0
  4 0 (nil) 0x7fb9f30b94a0
  ...

[akpm@linux-foundation.org: use SA_RESTORER for backportability]
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Emese Revfy <re.emese@gmail.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Julien Tinnes <jln@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2013-0914
CWE: CWE-264
Vulnerability description: The flush_signal_handlers function in kernel/signal.c in the Linux kernel before 3.8.4 preserves the value of the sa_restorer field across an exec operation, which makes it easier for local users to bypass the ASLR protection mechanism via a crafted application containing a sigaction system call.

Project: linux

flush_signal_handlers(struct task_struct *t, int force_default)
{
	int i;
	struct k_sigaction *ka = &t->sighand->action[0];
	for (i = _NSIG ; i != 0 ; i--) {
 		if (force_default || ka->sa.sa_handler != SIG_IGN)
 			ka->sa.sa_handler = SIG_DFL;
 		ka->sa.sa_flags = 0;
#ifdef SA_RESTORER
		ka->sa.sa_restorer = NULL;
#endif
 		sigemptyset(&ka->sa.sa_mask);
 		ka++;
 	}
}
Commit message: Bluetooth: Fix incorrect strncpy() in hidp_setup_hid()

The length parameter should be sizeof(req->name) - 1 because there is no
guarantee that string provided by userspace will contain the trailing
'\0'.

Can be easily reproduced by manually setting req->name to 128 non-zero
bytes prior to ioctl(HIDPCONNADD) and checking the device name setup on
input subsystem:

$ cat /sys/devices/pnp0/00\:04/tty/ttyS0/hci0/hci0\:1/input8/name
AAAAAA[...]AAAAAAAAf0:af:f0:af:f0:af

("f0:af:f0:af:f0:af" is the device bluetooth address, taken from "phys"
field in struct hid_device due to overflow.)

Cc: stable@vger.kernel.org
Signed-off-by: Anderson Lizardo <anderson.lizardo@openbossa.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
CVE: CVE-2013-0349
CWE: CWE-200
Vulnerability description: The hidp_setup_hid function in net/bluetooth/hidp/core.c in the Linux kernel before 3.7.6 does not properly copy a certain name field, which allows local users to obtain sensitive information from kernel memory by setting a long name and making an HIDPCONNADD ioctl call.

Project: linux
File: core.c

static int hidp_setup_hid(struct hidp_session *session,
				struct hidp_connadd_req *req)
{
	struct hid_device *hid;
	int err;

	session->rd_data = kzalloc(req->rd_size, GFP_KERNEL);
	if (!session->rd_data)
		return -ENOMEM;

	if (copy_from_user(session->rd_data, req->rd_data, req->rd_size)) {
		err = -EFAULT;
		goto fault;
	}
	session->rd_size = req->rd_size;

	hid = hid_allocate_device();
	if (IS_ERR(hid)) {
		err = PTR_ERR(hid);
		goto fault;
	}

	session->hid = hid;

	hid->driver_data = session;

	hid->bus     = BUS_BLUETOOTH;
	hid->vendor  = req->vendor;
	hid->product = req->product;
 	hid->version = req->version;
 	hid->country = req->country;
 
	strncpy(hid->name, req->name, sizeof(req->name) - 1);
 
 	snprintf(hid->phys, sizeof(hid->phys), "%pMR",
 		 &bt_sk(session->ctrl_sock->sk)->src);

	snprintf(hid->uniq, sizeof(hid->uniq), "%pMR",
		 &bt_sk(session->ctrl_sock->sk)->dst);

	hid->dev.parent = &session->conn->dev;
	hid->ll_driver = &hidp_hid_driver;

	hid->hid_get_raw_report = hidp_get_raw_report;
	hid->hid_output_raw_report = hidp_output_raw_report;

	/* True if device is blacklisted in drivers/hid/hid-core.c */
	if (hid_ignore(hid)) {
		hid_destroy_device(session->hid);
		session->hid = NULL;
		return -ENODEV;
	}

	return 0;

fault:
	kfree(session->rd_data);
	session->rd_data = NULL;

	return err;
}
Commit message: vhost: fix length for cross region descriptor

If a single descriptor crosses a region, the
second chunk length should be decremented
by size translated so far, instead it includes
the full descriptor length.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2013-0311
Vulnerability description: The translate_desc function in drivers/vhost/vhost.c in the Linux kernel before 3.7 does not properly handle cross-region descriptors, which allows guest OS users to obtain host OS privileges by leveraging KVM guest OS privileges.

Project: linux
File: vhost.c

static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
			  struct iovec iov[], int iov_size)
{
	const struct vhost_memory_region *reg;
	struct vhost_memory *mem;
	struct iovec *_iov;
	u64 s = 0;
	int ret = 0;

	rcu_read_lock();

	mem = rcu_dereference(dev->memory);
	while ((u64)len > s) {
		u64 size;
		if (unlikely(ret >= iov_size)) {
			ret = -ENOBUFS;
			break;
		}
		reg = find_region(mem, addr, len);
		if (unlikely(!reg)) {
			ret = -EFAULT;
			break;
 		}
 		_iov = iov + ret;
 		size = reg->memory_size - addr + reg->guest_phys_addr;
		_iov->iov_len = min((u64)len - s, size);
 		_iov->iov_base = (void __user *)(unsigned long)
 			(reg->userspace_addr + addr - reg->guest_phys_addr);
 		s += size;
		addr += size;
		++ret;
	}

	rcu_read_unlock();
	return ret;
}
Commit message: net: fix infinite loop in __skb_recv_datagram()

Tommi was fuzzing with trinity and reported the following problem :

commit 3f518bf745 (datagram: Add offset argument to __skb_recv_datagram)
missed that a raw socket receive queue can contain skbs with no payload.

We can loop in __skb_recv_datagram() with MSG_PEEK mode, because
wait_for_packet() is not prepared to skip these skbs.

[   83.541011] INFO: rcu_sched detected stalls on CPUs/tasks: {}
(detected by 0, t=26002 jiffies, g=27673, c=27672, q=75)
[   83.541011] INFO: Stall ended before state dump start
[  108.067010] BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child31:2847]
...
[  108.067010] Call Trace:
[  108.067010]  [<ffffffff818cc103>] __skb_recv_datagram+0x1a3/0x3b0
[  108.067010]  [<ffffffff818cc33d>] skb_recv_datagram+0x2d/0x30
[  108.067010]  [<ffffffff819ed43d>] rawv6_recvmsg+0xad/0x240
[  108.067010]  [<ffffffff818c4b04>] sock_common_recvmsg+0x34/0x50
[  108.067010]  [<ffffffff818bc8ec>] sock_recvmsg+0xbc/0xf0
[  108.067010]  [<ffffffff818bf31e>] sys_recvfrom+0xde/0x150
[  108.067010]  [<ffffffff81ca4329>] system_call_fastpath+0x16/0x1b

Reported-by: Tommi Rantala <tt.rantala@gmail.com>
Tested-by: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2013-0290
CWE: CWE-20
Vulnerability description: The __skb_recv_datagram function in net/core/datagram.c in the Linux kernel before 3.8 does not properly handle the MSG_PEEK flag with zero-length data, which allows local users to cause a denial of service (infinite loop and system hang) via a crafted application.

Project: linux

struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
				    int *peeked, int *off, int *err)
{
	struct sk_buff *skb;
	long timeo;
	/*
	 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
	 */
	int error = sock_error(sk);

	if (error)
		goto no_packet;

	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

	do {
		/* Again only user level code calls this function, so nothing
		 * interrupt level will suddenly eat the receive_queue.
		 *
		 * Look at current nfs client by the way...
		 * However, this function was correct in any case. 8)
		 */
		unsigned long cpu_flags;
		struct sk_buff_head *queue = &sk->sk_receive_queue;

		spin_lock_irqsave(&queue->lock, cpu_flags);
 		skb_queue_walk(queue, skb) {
 			*peeked = skb->peeked;
 			if (flags & MSG_PEEK) {
				if (*off >= skb->len && skb->len) {
 					*off -= skb->len;
 					continue;
 				}
				skb->peeked = 1;
				atomic_inc(&skb->users);
			} else
				__skb_unlink(skb, queue);

			spin_unlock_irqrestore(&queue->lock, cpu_flags);
			return skb;
		}
		spin_unlock_irqrestore(&queue->lock, cpu_flags);

		/* User doesn't want to wait */
		error = -EAGAIN;
		if (!timeo)
			goto no_packet;

	} while (!wait_for_packet(sk, err, &timeo));

	return NULL;

no_packet:
	*err = error;
	return NULL;
}