diff options
| author | Aleksa Sarai <aleksa@amutable.com> | 2026-04-01 01:46:21 +1100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-04-07 12:32:22 +0200 |
| commit | 97b67e64affb0e709eeecc50f6a9222fc20bd14b (patch) | |
| tree | 1de5b0c9bfb5b3c83721595b091d881540d893f9 | |
| parent | 4639f1cfba03e77e4fa2062cf904de63021fb746 (diff) | |
dcache: permit dynamic_dname()s up to NAME_MAX
dynamic_dname() has had an implicit limit of 64 characters since it was
introduced in commit c23fbb6bcb3e ("VFS: delay the dentry name
generation on sockets and pipes"), however it seems that this was a
fairly arbitrary number (suspiciously it was double the previously
hardcoded buffer size).
NAME_MAX seems like a more reasonable and consistent limit for d_name
lengths. While we're at it, we can also remove the unnecessary
stack-allocated array and just memmove() the formatted string to the end
of the buffer.
It should also be noted that at least one driver (in particular,
liveupdate's usage of anon_inode for session files) already exceeded
this limit without noticing that readlink(/proc/self/fd/$n) always
returns -ENAMETOOLONG, so this fixes those drivers as well.
Fixes: 0153094d03df ("liveupdate: luo_session: add sessions support")
Fixes: c23fbb6bcb3e ("VFS: delay the dentry name generation on sockets and pipes")
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
Link: https://patch.msgid.link/20260401-dynamic-dname-name_max-v1-1-8ca20ab2642e@amutable.com
Tested-by: Luca Boccassi <luca.boccassi@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/d_path.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/fs/d_path.c b/fs/d_path.c index bb365511066b..a48957c0971e 100644 --- a/fs/d_path.c +++ b/fs/d_path.c @@ -301,18 +301,19 @@ EXPORT_SYMBOL(d_path); char *dynamic_dname(char *buffer, int buflen, const char *fmt, ...) { va_list args; - char temp[64]; + char *start; int sz; va_start(args, fmt); - sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; + sz = vsnprintf(buffer, buflen, fmt, args) + 1; va_end(args); - if (sz > sizeof(temp) || sz > buflen) + if (sz > NAME_MAX || sz > buflen) return ERR_PTR(-ENAMETOOLONG); - buffer += buflen - sz; - return memcpy(buffer, temp, sz); + /* Move the formatted d_name to the end of the buffer. */ + start = buffer + (buflen - sz); + return memmove(start, buffer, sz); } char *simple_dname(struct dentry *dentry, char *buffer, int buflen) |