[PATCH] bitmap: parse input from kernel and user buffers
lib/bitmap.c:bitmap_parse() is a library function that received as input a
user buffer. This seemed to have originated from the way the write_proc
function of the /proc filesystem operates.
This has been reworked to not use kmalloc and eliminates a lot of
get_user() overhead by performing one access_ok before using __get_user().
We need to test if we are in kernel or user space (is_user) and access the
buffer differently. We cannot use __get_user() to access kernel addresses
in all cases, for example in architectures with separate address space for
kernel and user.
This function will be useful for other uses as well; for example, taking
input for /sysfs instead of /proc, so it was changed to accept kernel
buffers. We have this use for the Linux UWB project, as part as the
upcoming bandwidth allocator code.
Only a few routines used this function and they were changed too.
Signed-off-by: Reinette Chatre <reinette.chatre@linux.intel.com>
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Joe Korty <joe.korty@ccur.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/lib/bitmap.c b/lib/bitmap.c
index d71e38c..037fa9a 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -316,10 +316,11 @@
EXPORT_SYMBOL(bitmap_scnprintf);
/**
- * bitmap_parse - convert an ASCII hex string into a bitmap.
- * @ubuf: pointer to buffer in user space containing string.
- * @ubuflen: buffer size in bytes. If string is smaller than this
+ * __bitmap_parse - convert an ASCII hex string into a bitmap.
+ * @buf: pointer to buffer containing string.
+ * @buflen: buffer size in bytes. If string is smaller than this
* then it must be terminated with a \0.
+ * @is_user: location of buffer, 0 indicates kernel space
* @maskp: pointer to bitmap array that will contain result.
* @nmaskbits: size of bitmap, in bits.
*
@@ -330,11 +331,13 @@
* characters and for grouping errors such as "1,,5", ",44", "," and "".
* Leading and trailing whitespace accepted, but not embedded whitespace.
*/
-int bitmap_parse(const char __user *ubuf, unsigned int ubuflen,
- unsigned long *maskp, int nmaskbits)
+int __bitmap_parse(const char *buf, unsigned int buflen,
+ int is_user, unsigned long *maskp,
+ int nmaskbits)
{
int c, old_c, totaldigits, ndigits, nchunks, nbits;
u32 chunk;
+ const char __user *ubuf = buf;
bitmap_zero(maskp, nmaskbits);
@@ -343,11 +346,15 @@
chunk = ndigits = 0;
/* Get the next chunk of the bitmap */
- while (ubuflen) {
+ while (buflen) {
old_c = c;
- if (get_user(c, ubuf++))
- return -EFAULT;
- ubuflen--;
+ if (is_user) {
+ if (__get_user(c, ubuf++))
+ return -EFAULT;
+ }
+ else
+ c = *buf++;
+ buflen--;
if (isspace(c))
continue;
@@ -388,11 +395,36 @@
nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
if (nbits > nmaskbits)
return -EOVERFLOW;
- } while (ubuflen && c == ',');
+ } while (buflen && c == ',');
return 0;
}
-EXPORT_SYMBOL(bitmap_parse);
+EXPORT_SYMBOL(__bitmap_parse);
+
+/**
+ * bitmap_parse_user()
+ *
+ * @ubuf: pointer to user buffer containing string.
+ * @ulen: buffer size in bytes. If string is smaller than this
+ * then it must be terminated with a \0.
+ * @maskp: pointer to bitmap array that will contain result.
+ * @nmaskbits: size of bitmap, in bits.
+ *
+ * Wrapper for __bitmap_parse(), providing it with user buffer.
+ *
+ * We cannot have this as an inline function in bitmap.h because it needs
+ * linux/uaccess.h to get the access_ok() declaration and this causes
+ * cyclic dependencies.
+ */
+int bitmap_parse_user(const char __user *ubuf,
+ unsigned int ulen, unsigned long *maskp,
+ int nmaskbits)
+{
+ if (!access_ok(VERIFY_READ, ubuf, ulen))
+ return -EFAULT;
+ return __bitmap_parse((const char *)ubuf, ulen, 1, maskp, nmaskbits);
+}
+EXPORT_SYMBOL(bitmap_parse_user);
/*
* bscnl_emit(buf, buflen, rbot, rtop, bp)