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Subject[PATCH 1/4] devmem: check vmalloc address on kmem read/write
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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-mm.orig/drivers/char/mem.c 2010-01-11 10:22:35.000000000 +0800
+++ linux-mm/drivers/char/mem.c 2010-01-11 10:32:32.000000000 +0800
@@ -395,6 +395,7 @@ 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) {
@@ -441,12 +442,16 @@ static ssize_t read_kmem(struct file *fi
return -ENOMEM;
while (count > 0) {
sz = size_inside_page(p, count);
+ if (!is_vmalloc_or_module_addr((void *)p)) {
+ err = -ENXIO;
+ break;
+ }
sz = vread(kbuf, (char *)p, sz);
if (!sz)
break;
if (copy_to_user(buf, kbuf, sz)) {
- free_page((unsigned long)kbuf);
- return -EFAULT;
+ err = -EFAULT;
+ break;
}
count -= sz;
buf += sz;
@@ -455,8 +460,8 @@ static ssize_t read_kmem(struct file *fi
}
free_page((unsigned long)kbuf);
}
- *ppos = p;
- return read;
+ *ppos = p;
+ return read ? read : err;
}


@@ -520,6 +525,7 @@ static ssize_t write_kmem(struct file *
ssize_t wrote = 0;
ssize_t virtr = 0;
char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
+ int err = 0;

if (p < (unsigned long) high_memory) {
unsigned long to_write = min_t(unsigned long, count,
@@ -540,12 +546,14 @@ static ssize_t write_kmem(struct file *
unsigned long sz = size_inside_page(p, count);
unsigned long n;

+ if (!is_vmalloc_or_module_addr((void *)p)) {
+ err = -ENXIO;
+ break;
+ }
n = copy_from_user(kbuf, buf, sz);
if (n) {
- if (wrote + virtr)
- break;
- free_page((unsigned long)kbuf);
- return -EFAULT;
+ err = -EFAULT;
+ break;
}
sz = vwrite(kbuf, (char *)p, sz);
count -= sz;
@@ -556,8 +564,8 @@ 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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