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

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Message-Id: <20191020221742.5728-1-jsavitz@redhat.com>
Date:   Sun, 20 Oct 2019 18:17:42 -0400
From:   Joel Savitz <jsavitz@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Savitz <jsavitz@...hat.com>,
        Fabrizio D'Angelo <Fabrizio_Dangelo@...dent.uml.edu>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-fsdevel@...r.kernel.org, fedora-rpi@...glegroups.com
Subject: [PATCH] fs: proc: Clarify warnings for invalid proc dir names

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@...dent.uml.edu>
Signed-off-by: Joel Savitz <jsavitz@...hat.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