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orangefs: clean up debugfs
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We recently refactored the Orangefs debugfs code.
The refactor seemed to trigger dan.carpenter@oracle.com's
static tester to find a possible double-free in the code.

While designing the fix we saw a condition under which the
buffer being freed could also be overflowed.

We also realized how to rebuild the related debugfs file's
"contents" (a string) without deleting and re-creating the file.

This fix should eliminate the possible double-free, the
potential overflow and improve code readability.

Signed-off-by: Mike Marshall <hubcap@omnibond.com>
Signed-off-by: Martin Brandenburg <martin@omnibond.com>
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Mike Marshall committed Nov 7, 2016
1 parent 804b173 commit dc03362
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Showing 2 changed files with 68 additions and 85 deletions.
147 changes: 64 additions & 83 deletions fs/orangefs/orangefs-debugfs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,9 @@ static struct client_debug_mask client_debug_mask;
*/
static DEFINE_MUTEX(orangefs_debug_lock);

/* Used to protect data in ORANGEFS_KMOD_DEBUG_HELP_FILE */
static DEFINE_MUTEX(orangefs_help_file_lock);

/*
* initialize kmod debug operations, create orangefs debugfs dir and
* ORANGEFS_KMOD_DEBUG_HELP_FILE.
Expand Down Expand Up @@ -289,6 +292,8 @@ static void *help_start(struct seq_file *m, loff_t *pos)

gossip_debug(GOSSIP_DEBUGFS_DEBUG, "help_start: start\n");

mutex_lock(&orangefs_help_file_lock);

if (*pos == 0)
payload = m->private;

Expand All @@ -305,6 +310,7 @@ static void *help_next(struct seq_file *m, void *v, loff_t *pos)
static void help_stop(struct seq_file *m, void *p)
{
gossip_debug(GOSSIP_DEBUGFS_DEBUG, "help_stop: start\n");
mutex_unlock(&orangefs_help_file_lock);
}

static int help_show(struct seq_file *m, void *v)
Expand Down Expand Up @@ -610,32 +616,54 @@ static int orangefs_prepare_cdm_array(char *debug_array_string)
* /sys/kernel/debug/orangefs/debug-help can be catted to
* see all the available kernel and client debug keywords.
*
* When the kernel boots, we have no idea what keywords the
* When orangefs.ko initializes, we have no idea what keywords the
* client supports, nor their associated masks.
*
* We pass through this function once at boot and stamp a
* We pass through this function once at module-load and stamp a
* boilerplate "we don't know" message for the client in the
* debug-help file. We pass through here again when the client
* starts and then we can fill out the debug-help file fully.
*
* The client might be restarted any number of times between
* reboots, we only build the debug-help file the first time.
* module reloads, we only build the debug-help file the first time.
*/
int orangefs_prepare_debugfs_help_string(int at_boot)
{
int rc = -EINVAL;
int i;
int byte_count = 0;
char *client_title = "Client Debug Keywords:\n";
char *kernel_title = "Kernel Debug Keywords:\n";
size_t string_size = DEBUG_HELP_STRING_SIZE;
size_t result_size;
size_t i;
char *new;
int rc = -EINVAL;

gossip_debug(GOSSIP_UTILS_DEBUG, "%s: start\n", __func__);

if (at_boot) {
byte_count += strlen(HELP_STRING_UNINITIALIZED);
if (at_boot)
client_title = HELP_STRING_UNINITIALIZED;
} else {
/*

/* build a new debug_help_string. */
new = kzalloc(DEBUG_HELP_STRING_SIZE, GFP_KERNEL);
if (!new) {
rc = -ENOMEM;
goto out;
}

/*
* strlcat(dst, src, size) will append at most
* "size - strlen(dst) - 1" bytes of src onto dst,
* null terminating the result, and return the total
* length of the string it tried to create.
*
* We'll just plow through here building our new debug
* help string and let strlcat take care of assuring that
* dst doesn't overflow.
*/
strlcat(new, client_title, string_size);

if (!at_boot) {

/*
* fill the client keyword/mask array and remember
* how many elements there were.
*/
Expand All @@ -644,64 +672,40 @@ int orangefs_prepare_debugfs_help_string(int at_boot)
if (cdm_element_count <= 0)
goto out;

/* Count the bytes destined for debug_help_string. */
byte_count += strlen(client_title);

for (i = 0; i < cdm_element_count; i++) {
byte_count += strlen(cdm_array[i].keyword + 2);
if (byte_count >= DEBUG_HELP_STRING_SIZE) {
pr_info("%s: overflow 1!\n", __func__);
goto out;
}
strlcat(new, "\t", string_size);
strlcat(new, cdm_array[i].keyword, string_size);
strlcat(new, "\n", string_size);
}

gossip_debug(GOSSIP_UTILS_DEBUG,
"%s: cdm_element_count:%d:\n",
__func__,
cdm_element_count);
}

byte_count += strlen(kernel_title);
strlcat(new, "\n", string_size);
strlcat(new, kernel_title, string_size);

for (i = 0; i < num_kmod_keyword_mask_map; i++) {
byte_count +=
strlen(s_kmod_keyword_mask_map[i].keyword + 2);
if (byte_count >= DEBUG_HELP_STRING_SIZE) {
pr_info("%s: overflow 2!\n", __func__);
goto out;
}
strlcat(new, "\t", string_size);
strlcat(new, s_kmod_keyword_mask_map[i].keyword, string_size);
result_size = strlcat(new, "\n", string_size);
}

/* build debug_help_string. */
debug_help_string = kzalloc(DEBUG_HELP_STRING_SIZE, GFP_KERNEL);
if (!debug_help_string) {
rc = -ENOMEM;
/* See if we tried to put too many bytes into "new"... */
if (result_size >= string_size) {
kfree(new);
goto out;
}

strcat(debug_help_string, client_title);

if (!at_boot) {
for (i = 0; i < cdm_element_count; i++) {
strcat(debug_help_string, "\t");
strcat(debug_help_string, cdm_array[i].keyword);
strcat(debug_help_string, "\n");
}
}

strcat(debug_help_string, "\n");
strcat(debug_help_string, kernel_title);

for (i = 0; i < num_kmod_keyword_mask_map; i++) {
strcat(debug_help_string, "\t");
strcat(debug_help_string, s_kmod_keyword_mask_map[i].keyword);
strcat(debug_help_string, "\n");
if (at_boot) {
debug_help_string = new;
} else {
mutex_lock(&orangefs_help_file_lock);
memset(debug_help_string, 0, DEBUG_HELP_STRING_SIZE);
strlcat(debug_help_string, new, string_size);
mutex_unlock(&orangefs_help_file_lock);
}

rc = 0;

out:

return rc;
out: return rc;

}

Expand Down Expand Up @@ -959,8 +963,12 @@ int orangefs_debugfs_new_client_string(void __user *arg)
ret = copy_from_user(&client_debug_array_string,
(void __user *)arg,
ORANGEFS_MAX_DEBUG_STRING_LEN);
if (ret != 0)

if (ret != 0) {
pr_info("%s: CLIENT_STRING: copy_from_user failed\n",
__func__);
return -EIO;
}

/*
* The real client-core makes an effort to ensure
Expand All @@ -975,45 +983,18 @@ int orangefs_debugfs_new_client_string(void __user *arg)
client_debug_array_string[ORANGEFS_MAX_DEBUG_STRING_LEN - 1] =
'\0';

if (ret != 0) {
pr_info("%s: CLIENT_STRING: copy_from_user failed\n",
__func__);
return -EIO;
}

pr_info("%s: client debug array string has been received.\n",
__func__);

if (!help_string_initialized) {

/* Free the "we don't know yet" default string... */
kfree(debug_help_string);

/* build a proper debug help string */
/* Build a proper debug help string. */
if (orangefs_prepare_debugfs_help_string(0)) {
gossip_err("%s: no debug help string \n",
__func__);
return -EIO;
}

/* Replace the boilerplate boot-time debug-help file. */
debugfs_remove(help_file_dentry);

help_file_dentry =
debugfs_create_file(
ORANGEFS_KMOD_DEBUG_HELP_FILE,
0444,
debug_dir,
debug_help_string,
&debug_help_fops);

if (!help_file_dentry) {
gossip_err("%s: debugfs_create_file failed for"
" :%s:!\n",
__func__,
ORANGEFS_KMOD_DEBUG_HELP_FILE);
return -EIO;
}
}

debug_mask_to_string(&client_debug_mask, 1);
Expand Down
6 changes: 4 additions & 2 deletions fs/orangefs/orangefs-mod.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,7 @@ static int __init orangefs_init(void)
* unknown at boot time.
*
* orangefs_prepare_debugfs_help_string will be used again
* later to rebuild the debug-help file after the client starts
* later to rebuild the debug-help-string after the client starts
* and passes along the needed info. The argument signifies
* which time orangefs_prepare_debugfs_help_string is being
* called.
Expand Down Expand Up @@ -152,7 +152,9 @@ static int __init orangefs_init(void)

ret = register_filesystem(&orangefs_fs_type);
if (ret == 0) {
pr_info("orangefs: module version %s loaded\n", ORANGEFS_VERSION);
pr_info("%s: module version %s loaded\n",
__func__,
ORANGEFS_VERSION);
ret = 0;
goto out;
}
Expand Down

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