proc: fix to check name length in proc_lookup_de()
Commit Message
__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@kernel.org>
---
fs/proc/generic.c | 5 ++++-
fs/proc/internal.h | 3 +++
2 files changed, 7 insertions(+), 1 deletion(-)
Comments
On Tue, Jan 10, 2023 at 11:21:12PM +0800, Chao Yu wrote:
> __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.
Both returns are correct and this is trading one errno for another.
> --- 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);
On 2023/1/11 2:01, Alexey Dobriyan wrote:
> On Tue, Jan 10, 2023 at 11:21:12PM +0800, Chao Yu wrote:
>> __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.
>
> Both returns are correct and this is trading one errno for another.
Oh, but it looks ENOENT is a little bit ambiguity, it may indicate file name
length is valid for procfs, but the entry is not exist.
This change is trying to make lookup logic keeping align w/ most other
filesystems' behavior. Also it can avoid running into unneeded lookup logic
in proc_lookup_de() for such ENAMETOOLONG case.
How do you think? :)
Thanks,
>
>> --- 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);
@@ -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;
}
@@ -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
*/