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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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