linux-kernel - [PATCH] proc: fix to check name length in proc_lookup

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Message-Id: <20230110152112.1119517-1-chao@kernel.org>
Date:   Tue, 10 Jan 2023 23:21:12 +0800
From:   Chao Yu <chao@...nel.org>
To:     akpm@...ux-foundation.org, adobriyan@...il.com
Cc:     viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Chao Yu <chao@...nel.org>
Subject: [PATCH] proc: fix to check name length in proc_lookup_de()

__proc_create() has limited dirent's max name length with 255, let's
add this limitation in proc_lookup_de(), so that it can return
-ENAMETOOLONG correctly instead of -ENOENT when stating a file which
has out-of-range name length.

Signed-off-by: Chao Yu <chao@...nel.org>
---
 fs/proc/generic.c  | 5 ++++-
 fs/proc/internal.h | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 587b91d9d998..5f52f20d5ed1 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -246,6 +246,9 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
 {
 	struct inode *inode;
 
+	if (dentry->d_name.len > PROC_NAME_LEN)
+		return ERR_PTR(-ENAMETOOLONG);
+
 	read_lock(&proc_subdir_lock);
 	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
 	if (de) {
@@ -402,7 +405,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 		goto out;
 	qstr.name = fn;
 	qstr.len = strlen(fn);
-	if (qstr.len == 0 || qstr.len >= 256) {
+	if (qstr.len == 0 || qstr.len > PROC_NAME_LEN) {
 		WARN(1, "name len %u\n", qstr.len);
 		return NULL;
 	}
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index b701d0207edf..7611bc684d9e 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -142,6 +142,9 @@ unsigned name_to_int(const struct qstr *qstr);
 /* Worst case buffer size needed for holding an integer. */
 #define PROC_NUMBUF 13
 
+/* Max name length of procfs dirent */
+#define PROC_NAME_LEN		255
+
 /*
  * array.c
  */
-- 
2.25.1