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    Subject[PATCH 3.16.y-ckt 89/94] ppp, slip: Validate VJ compression slot parameters completely
    Date
    3.16.7-ckt20 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ben Hutchings <ben@decadent.org.uk>

    commit 4ab42d78e37a294ac7bc56901d563c642e03c4ae upstream.

    Currently slhc_init() treats out-of-range values of rslots and tslots
    as equivalent to 0, except that if tslots is too large it will
    dereference a null pointer (CVE-2015-7799).

    Add a range-check at the top of the function and make it return an
    ERR_PTR() on error instead of NULL. Change the callers accordingly.

    Compile-tested only.

    Reported-by: 郭永刚 <guoyonggang@360.cn>
    References: http://article.gmane.org/gmane.comp.security.oss.general/17908
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Cc: Moritz Mühlenhoff <jmm@inutil.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/isdn/i4l/isdn_ppp.c | 10 ++++------
    drivers/net/ppp/ppp_generic.c | 6 ++----
    drivers/net/slip/slhc.c | 12 ++++++++----
    drivers/net/slip/slip.c | 2 +-
    4 files changed, 15 insertions(+), 15 deletions(-)

    diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
    index 29d1cc0b2bc4..1025ef1a3988 100644
    --- a/drivers/isdn/i4l/isdn_ppp.c
    +++ b/drivers/isdn/i4l/isdn_ppp.c
    @@ -322,9 +322,9 @@ isdn_ppp_open(int min, struct file *file)
    * VJ header compression init
    */
    is->slcomp = slhc_init(16, 16); /* not necessary for 2. link in bundle */
    - if (!is->slcomp) {
    + if (IS_ERR(is->slcomp)) {
    isdn_ppp_ccp_reset_free(is);
    - return -ENOMEM;
    + return PTR_ERR(is->slcomp);
    }
    #endif
    #ifdef CONFIG_IPPP_FILTER
    @@ -573,10 +573,8 @@ isdn_ppp_ioctl(int min, struct file *file, unsigned int cmd, unsigned long arg)
    is->maxcid = val;
    #ifdef CONFIG_ISDN_PPP_VJ
    sltmp = slhc_init(16, val);
    - if (!sltmp) {
    - printk(KERN_ERR "ippp, can't realloc slhc struct\n");
    - return -ENOMEM;
    - }
    + if (IS_ERR(sltmp))
    + return PTR_ERR(sltmp);
    if (is->slcomp)
    slhc_free(is->slcomp);
    is->slcomp = sltmp;
    diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
    index dbf56debb7e3..65edd34654ee 100644
    --- a/drivers/net/ppp/ppp_generic.c
    +++ b/drivers/net/ppp/ppp_generic.c
    @@ -709,10 +709,8 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    val &= 0xffff;
    }
    vj = slhc_init(val2+1, val+1);
    - if (!vj) {
    - netdev_err(ppp->dev,
    - "PPP: no memory (VJ compressor)\n");
    - err = -ENOMEM;
    + if (IS_ERR(vj)) {
    + err = PTR_ERR(vj);
    break;
    }
    ppp_lock(ppp);
    diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c
    index 1252d9c726a7..b52eabc168a0 100644
    --- a/drivers/net/slip/slhc.c
    +++ b/drivers/net/slip/slhc.c
    @@ -84,8 +84,9 @@ static long decode(unsigned char **cpp);
    static unsigned char * put16(unsigned char *cp, unsigned short x);
    static unsigned short pull16(unsigned char **cpp);

    -/* Initialize compression data structure
    +/* Allocate compression data structure
    * slots must be in range 0 to 255 (zero meaning no compression)
    + * Returns pointer to structure or ERR_PTR() on error.
    */
    struct slcompress *
    slhc_init(int rslots, int tslots)
    @@ -94,11 +95,14 @@ slhc_init(int rslots, int tslots)
    register struct cstate *ts;
    struct slcompress *comp;

    + if (rslots < 0 || rslots > 255 || tslots < 0 || tslots > 255)
    + return ERR_PTR(-EINVAL);
    +
    comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
    if (! comp)
    goto out_fail;

    - if ( rslots > 0 && rslots < 256 ) {
    + if (rslots > 0) {
    size_t rsize = rslots * sizeof(struct cstate);
    comp->rstate = kzalloc(rsize, GFP_KERNEL);
    if (! comp->rstate)
    @@ -106,7 +110,7 @@ slhc_init(int rslots, int tslots)
    comp->rslot_limit = rslots - 1;
    }

    - if ( tslots > 0 && tslots < 256 ) {
    + if (tslots > 0) {
    size_t tsize = tslots * sizeof(struct cstate);
    comp->tstate = kzalloc(tsize, GFP_KERNEL);
    if (! comp->tstate)
    @@ -141,7 +145,7 @@ out_free2:
    out_free:
    kfree(comp);
    out_fail:
    - return NULL;
    + return ERR_PTR(-ENOMEM);
    }


    diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
    index 87526443841f..0641fccdc954 100644
    --- a/drivers/net/slip/slip.c
    +++ b/drivers/net/slip/slip.c
    @@ -164,7 +164,7 @@ static int sl_alloc_bufs(struct slip *sl, int mtu)
    if (cbuff == NULL)
    goto err_exit;
    slcomp = slhc_init(16, 16);
    - if (slcomp == NULL)
    + if (IS_ERR(slcomp))
    goto err_exit;
    #endif
    spin_lock_bh(&sl->lock);

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