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Date: Sun, 22 Jan 2012 10:46:45 -0800
From: Earl Chew <echew@...acom.com>
To: Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>,
Eric Paris <eparis@...hat.com>,
"Serge E. Hallyn" <serge.hallyn@...onical.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
<adobriyan@...il.com>
Subject: [PATCH] Support single byte reads from integers published in procfs
by kernel/sysctl.c
The following illustrates the problem:
cat /proc/sys/kernel/threads-max | od -bc
0000000 065 062 071 071 062 012
5 2 9 9 2 \n
0000006
dd bs=1 < /proc/sys/kernel/threads-max | od -bc
1+0 records in
1+0 records out
1 byte (1 B) copied, 0.000102707 s, 9.7 kB/s
0000000 065
5
0000001
The implementation in sysctl.c is inconsistent because support
for small reads is available for strings (eg /proc/sys/kernel/core_pattern),
but not integers.
This issue was also reported in:
https://bugzilla.kernel.org/show_bug.cgi?id=19182
Signed-off-by: Earl Chew <echew@...acom.com>
---
kernel/sysctl.c | 83 +++++++++++++++++++++++++++++++++++++-----------------
1 files changed, 57 insertions(+), 26 deletions(-)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ae27196..b13d47b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2215,31 +2215,41 @@ static int proc_get_long(char **buf, size_t *size,
* @size: the size of the user buffer
* @val: the integer to be converted
* @neg: sign of the number, %TRUE for negative
+ * @skip: the number of characters to skip
*
* In case of success %0 is returned and @buf and @size are updated with
* the amount of bytes written.
*/
static int proc_put_long(void __user **buf, size_t *size, unsigned long val,
- bool neg)
+ bool neg, loff_t *skip)
{
int len;
char tmp[TMPBUFLEN], *p = tmp;
sprintf(p, "%s%lu", neg ? "-" : "", val);
- len = strlen(tmp);
- if (len > *size)
- len = *size;
- if (copy_to_user(*buf, tmp, len))
- return -EFAULT;
- *size -= len;
- *buf += len;
+ len = strlen(p);
+ if (*skip >= len) {
+ *skip -= len;
+ } else {
+ p += *skip;
+ len -= *skip;
+ *skip = 0;
+ if (len > *size)
+ len = *size;
+ if (copy_to_user(*buf, p, len))
+ return -EFAULT;
+ *size -= len;
+ *buf += len;
+ }
return 0;
}
#undef TMPBUFLEN
-static int proc_put_char(void __user **buf, size_t *size, char c)
+static int proc_put_char(void __user **buf, size_t *size, char c, loff_t *skip)
{
- if (*size) {
+ if (*skip) {
+ (*skip)--;
+ } else if (*size) {
char __user **buffer = (char __user **)buf;
if (put_user(c, *buffer))
return -EFAULT;
@@ -2279,10 +2289,11 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
{
int *i, vleft, first = 1, err = 0;
unsigned long page = 0;
+ loff_t skip = *ppos;
size_t left;
char *kbuf;
- if (!tbl_data || !table->maxlen || !*lenp || (*ppos && !write)) {
+ if (!tbl_data || !table->maxlen || !*lenp) {
*lenp = 0;
return 0;
}
@@ -2331,18 +2342,26 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
err = -EINVAL;
break;
}
- if (!first)
- err = proc_put_char(&buffer, &left, '\t');
+ if (!first) {
+ err = proc_put_char(
+ &buffer, &left, '\t', &skip);
+ }
if (err)
break;
- err = proc_put_long(&buffer, &left, lval, neg);
+ err = proc_put_long(&buffer, &left, lval, neg, &skip);
if (err)
break;
}
}
- if (!write && !first && left && !err)
- err = proc_put_char(&buffer, &left, '\n');
+ if (!write) {
+ if (!first && !err)
+ err = proc_put_char(&buffer, &left, '\n', &skip);
+ if (!err && skip) {
+ *lenp = 0;
+ return 0;
+ }
+ }
if (write && !err && left)
left -= proc_skip_spaces(&kbuf);
free:
@@ -2497,10 +2516,11 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
unsigned long *i, *min, *max;
int vleft, first = 1, err = 0;
unsigned long page = 0;
+ loff_t skip = *ppos;
size_t left;
char *kbuf;
- if (!data || !table->maxlen || !*lenp || (*ppos && !write)) {
+ if (!data || !table->maxlen || !*lenp) {
*lenp = 0;
return 0;
}
@@ -2546,15 +2566,22 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
} else {
val = convdiv * (*i) / convmul;
if (!first)
- err = proc_put_char(&buffer, &left, '\t');
- err = proc_put_long(&buffer, &left, val, false);
+ err = proc_put_char(
+ &buffer, &left, '\t', &skip);
+ err = proc_put_long(&buffer, &left, val, false, &skip);
if (err)
break;
}
}
- if (!write && !first && left && !err)
- err = proc_put_char(&buffer, &left, '\n');
+ if (!write) {
+ if (!first && !err)
+ err = proc_put_char(&buffer, &left, '\n', &skip);
+ if (!err && skip) {
+ *lenp = 0;
+ return 0;
+ }
+ }
if (write && !err)
left -= proc_skip_spaces(&kbuf);
free:
@@ -2805,6 +2832,7 @@ int proc_do_large_bitmap(struct ctl_table *table, int write,
int err = 0;
bool first = 1;
size_t left = *lenp;
+ loff_t skip = *ppos;
unsigned long bitmap_len = table->maxlen;
unsigned long *bitmap = (unsigned long *) table->data;
unsigned long *tmp_bitmap = NULL;
@@ -2893,18 +2921,21 @@ int proc_do_large_bitmap(struct ctl_table *table, int write,
bit_a + 1) - 1;
if (!first) {
- err = proc_put_char(&buffer, &left, ',');
+ err = proc_put_char(&buffer, &left, ',', &skip);
if (err)
break;
}
- err = proc_put_long(&buffer, &left, bit_a, false);
+ err = proc_put_long(
+ &buffer, &left, bit_a, false, &skip);
if (err)
break;
if (bit_a != bit_b) {
- err = proc_put_char(&buffer, &left, '-');
+ err = proc_put_char(
+ &buffer, &left, '-', &skip);
if (err)
break;
- err = proc_put_long(&buffer, &left, bit_b, false);
+ err = proc_put_long(
+ &buffer, &left, bit_b, false, &skip);
if (err)
break;
}
@@ -2912,7 +2943,7 @@ int proc_do_large_bitmap(struct ctl_table *table, int write,
first = 0; bit_b++;
}
if (!err)
- err = proc_put_char(&buffer, &left, '\n');
+ err = proc_put_char(&buffer, &left, '\n', &skip);
}
if (!err) {
--
1.6.5.2
--
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