[PATCH] fs: proc: Clarify warnings for invalid proc dir names

[PATCH] fs: proc: Clarify warnings for invalid proc dir names

[Joel Savitz]

When one attempts to create a directory in /proc with an invalid name,
such as one in a subdirectory that doesn't exist, one with a name beyond
256 characters, or a reserved name such as '.' or '..', the kernel
throws a warning message that looks like this:

	[ 7913.252558] name 'invalid_name'

This warning message is nearly the same for all invalid cases, including
the removal of a nonexistent directory. This patch clarifies the warning
message and differentiates the invalid creation/removal cases so as to
allow the user to more quickly understand their mistake.

Signed-off-by: Fabrizio D'Angelo <Fabrizio_Dangelo@student.uml.edu>
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
---
 fs/proc/generic.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 64e9ee1b129e..df04fd4f02af 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -173,7 +173,7 @@ static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
 		len = next - cp;
 		de = pde_subdir_find(de, cp, len);
 		if (!de) {
-			WARN(1, "name '%s'\n", name);
+			WARN(1, "invalid proc dir name '%s'\n", name);
 			return -ENOENT;
 		}
 		cp += len + 1;
@@ -386,15 +386,15 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 	qstr.name = fn;
 	qstr.len = strlen(fn);
 	if (qstr.len == 0 || qstr.len >= 256) {
-		WARN(1, "name len %u\n", qstr.len);
+		WARN(1, "invalid proc dir name len %u\n", qstr.len);
 		return NULL;
 	}
 	if (qstr.len == 1 && fn[0] == '.') {
-		WARN(1, "name '.'\n");
+		WARN(1, "invalid proc dir name '.'\n");
 		return NULL;
 	}
 	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
-		WARN(1, "name '..'\n");
+		WARN(1, "invalid proc dir name '..'\n");
 		return NULL;
 	}
 	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
@@ -402,7 +402,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 		return NULL;
 	}
 	if (is_empty_pde(*parent)) {
-		WARN(1, "attempt to add to permanently empty directory");
+		WARN(1, "attempt to add to permanently empty directory in proc");
 		return NULL;
 	}
 
@@ -670,7 +670,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
 		rb_erase(&de->subdir_node, &parent->subdir);
 	write_unlock(&proc_subdir_lock);
 	if (!de) {
-		WARN(1, "name '%s'\n", name);
+		WARN(1, "unable to remove nonexistent proc dir '%s'\n", name);
 		return;
 	}
 
-- 
2.23.0

Re: [PATCH] fs: proc: Clarify warnings for invalid proc dir names

[Alexey Dobriyan]

On Sun, Oct 20, 2019 at 06:17:42PM -0400, Joel Savitz wrote:
> When one attempts to create a directory in /proc with an invalid name,
> such as one in a subdirectory that doesn't exist, one with a name beyond
> 256 characters, or a reserved name such as '.' or '..', the kernel
> throws a warning message that looks like this:
> 
> 	[ 7913.252558] name 'invalid_name'

Yes, the important part is filename:line which uniquely identifies
the issue.

> This warning message is nearly the same for all invalid cases, including
> the removal of a nonexistent directory. This patch clarifies the warning
> message and differentiates the invalid creation/removal cases so as to
> allow the user to more quickly understand their mistake.

> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -173,7 +173,7 @@ static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
>  		len = next - cp;
>  		de = pde_subdir_find(de, cp, len);
>  		if (!de) {
> -			WARN(1, "name '%s'\n", name);
> +			WARN(1, "invalid proc dir name '%s'\n", name);

Wrong string anyway, this is nonexistent name, directory or not.

> -		WARN(1, "name len %u\n", qstr.len);
> +		WARN(1, "invalid proc dir name len %u\n", qstr.len);
>  		return NULL;
>  	}
>  	if (qstr.len == 1 && fn[0] == '.') {
> -		WARN(1, "name '.'\n");
> +		WARN(1, "invalid proc dir name '.'\n");
>  		return NULL;
>  	}
>  	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
> -		WARN(1, "name '..'\n");
> +		WARN(1, "invalid proc dir name '..'\n");
>  		return NULL;
>  	}
>  	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
> @@ -402,7 +402,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
>  		return NULL;
>  	}
>  	if (is_empty_pde(*parent)) {
> -		WARN(1, "attempt to add to permanently empty directory");
> +		WARN(1, "attempt to add to permanently empty directory in proc");

"proc" will be spilled over all backtrace.

> @@ -670,7 +670,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
>  		rb_erase(&de->subdir_node, &parent->subdir);
>  	write_unlock(&proc_subdir_lock);
>  	if (!de) {
> -		WARN(1, "name '%s'\n", name);
> +		WARN(1, "unable to remove nonexistent proc dir '%s'\n", name);

I'm not sure if such chatty strings are necessary.