[PATCH 2/2] x86/resctrl: Use appropriate API for strings terminated by newline

Reinette Chatre
2020-04-01T18:31:04Z

The user input to files in the resctrl filesystem are expected to be
terminated with a newline. Testing the user input includes a test for
the presence of a newline and then replacing the newline with NUL
byte followed by comparison using strcmp().

sysfs_streq() exists to test if strings are equal, treating both NUL and
newline-then-NUL as equivalent string terminations. Even more,
sysfs_match_string() exists to match a given string in an array using
sysfs_streq().

Replace existing strcmp() comparisons of strings that are terminated
with a newline with more appropriate sysfs_streq() via the
sysfs_match_string() API that can perform the match across the different
mode strings that are already maintained in an array.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index fbee891a7d6e..623e33c0a290 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1412,11 +1412,11 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
struct rdtgroup *rdtgrp;
enum rdtgrp_mode mode;
int ret = 0;
+ int user_m;

/* Valid input requires a trailing newline */
if (nbytes == 0 || buf[nbytes - 1] != '\n')
return -EINVAL;
- buf[nbytes - 1] = '\0';

rdtgrp = rdtgroup_kn_lock_live(of->kn);
if (!rdtgrp) {
@@ -1428,11 +1428,15 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,

mode = rdtgrp->mode;

- if ((!strcmp(buf, "shareable") && mode == RDT_MODE_SHAREABLE) ||
- (!strcmp(buf, "exclusive") && mode == RDT_MODE_EXCLUSIVE) ||
- (!strcmp(buf, "pseudo-locksetup") &&
- mode == RDT_MODE_PSEUDO_LOCKSETUP) ||
- (!strcmp(buf, "pseudo-locked") && mode == RDT_MODE_PSEUDO_LOCKED))
+ user_m = sysfs_match_string(rdt_mode_str, buf);
+ if (user_m < 0) {
+ rdt_last_cmd_puts("Unknown or unsupported mode\n");
+ ret = user_m;
+ goto out;
+ }
+
+ /* Do nothing and return success if user asks for current mode */
+ if (user_m == mode)
goto out;

if (mode == RDT_MODE_PSEUDO_LOCKED) {
@@ -1441,14 +1445,14 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
goto out;
}

- if (!strcmp(buf, "shareable")) {
+ if (user_m == RDT_MODE_SHAREABLE) {
if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
ret = rdtgroup_locksetup_exit(rdtgrp);
if (ret)
goto out;
}
rdtgrp->mode = RDT_MODE_SHAREABLE;
- } else if (!strcmp(buf, "exclusive")) {
+ } else if (user_m == RDT_MODE_EXCLUSIVE) {
if (!rdtgroup_mode_test_exclusive(rdtgrp)) {
ret = -EINVAL;
goto out;
@@ -1459,14 +1463,11 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
goto out;
}
rdtgrp->mode = RDT_MODE_EXCLUSIVE;
- } else if (!strcmp(buf, "pseudo-locksetup")) {
+ } else if (user_m == RDT_MODE_PSEUDO_LOCKSETUP) {
ret = rdtgroup_locksetup_enter(rdtgrp);
if (ret)
goto out;
rdtgrp->mode = RDT_MODE_PSEUDO_LOCKSETUP;
- } else {
- rdt_last_cmd_puts("Unknown or unsupported mode\n");
- ret = -EINVAL;
}

out:
--
2.21.0