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    Subject[stable] [PATCH] devmem: check vmalloc address on kmem read/write
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    commit 325fda71d0badc1073dc59f12a948f24ff05796a upstream.

    Otherwise vmalloc_to_page() will BUG().

    This also makes the kmem read/write implementation aligned with mem(4):
    "References to nonexistent locations cause errors to be returned." Here
    we return -ENXIO (inspired by Hugh) if no bytes have been transfered
    to/from user space, otherwise return partial read/write results.

    CC: Greg Kroah-Hartman <gregkh@suse.de>
    CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>
    CC: <stable@kernel.org>
    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    drivers/char/mem.c | 28 ++++++++++++++++++----------
    1 file changed, 18 insertions(+), 10 deletions(-)

    --- linux-2.6.32.orig/drivers/char/mem.c 2010-02-04 10:28:19.000000000 +0800
    +++ linux-2.6.32/drivers/char/mem.c 2010-02-04 10:37:55.000000000 +0800
    @@ -408,6 +408,7 @@ static ssize_t read_kmem(struct file *fi
    unsigned long p = *ppos;
    ssize_t low_count, read, sz;
    char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
    + int err = 0;

    read = 0;
    if (p < (unsigned long) high_memory) {
    @@ -464,14 +465,18 @@ static ssize_t read_kmem(struct file *fi
    while (count > 0) {
    int len = count;

    + if (!is_vmalloc_or_module_addr((void *)p)) {
    + err = -ENXIO;
    + break;
    + }
    if (len > PAGE_SIZE)
    len = PAGE_SIZE;
    len = vread(kbuf, (char *)p, len);
    if (!len)
    break;
    if (copy_to_user(buf, kbuf, len)) {
    - free_page((unsigned long)kbuf);
    - return -EFAULT;
    + err = -EFAULT;
    + break;
    }
    count -= len;
    buf += len;
    @@ -480,8 +485,8 @@ static ssize_t read_kmem(struct file *fi
    }
    free_page((unsigned long)kbuf);
    }
    - *ppos = p;
    - return read;
    + *ppos = p;
    + return read ? read : err;
    }


    @@ -557,6 +562,7 @@ static ssize_t write_kmem(struct file *
    ssize_t virtr = 0;
    ssize_t written;
    char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
    + int err = 0;

    if (p < (unsigned long) high_memory) {

    @@ -580,15 +586,17 @@ static ssize_t write_kmem(struct file *
    while (count > 0) {
    int len = count;

    + if (!is_vmalloc_or_module_addr((void *)p)) {
    + err = -ENXIO;
    + break;
    + }
    if (len > PAGE_SIZE)
    len = PAGE_SIZE;
    if (len) {
    written = copy_from_user(kbuf, buf, len);
    if (written) {
    - if (wrote + virtr)
    - break;
    - free_page((unsigned long)kbuf);
    - return -EFAULT;
    + err = -EFAULT;
    + break;
    }
    }
    len = vwrite(kbuf, (char *)p, len);
    @@ -600,8 +608,8 @@ static ssize_t write_kmem(struct file *
    free_page((unsigned long)kbuf);
    }

    - *ppos = p;
    - return virtr + wrote;
    + *ppos = p;
    + return virtr + wrote ? : err;
    }
    #endif


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