Re: [PATCH v3 3/3] 9p: skip over-long directory entry names for legacy 9p2000 too
From: Christian Schoenebeck <linux_oss@crudebyte.com>
Date: 2026-09-18 12:08:08
Also in:
linux-fsdevel, lkml, v9fs
On Friday, 18 September 2026 04:48:51 CEST Haobin Wu wrote:
The legacy 9p2000 and 9p2000.u readdir path, v9fs_dir_readdir(), parses each entry with p9stat_read() and, unlike the 9p2000.L path, never had a 256-byte name limit: a name of any length up to the wire maximum was handed to dir_emit(). getdents64() therefore returned names longer than NAME_MAX that no later syscall can use, and failed with -EIO for names of PATH_MAX bytes or more. Apply the same NAME_MAX check as the previous patch does for v9fs_dir_readdir_dotl(), so both protocol variants behave the same. Note that this is a behaviour change for 9p2000 and 9p2000.u: entries with names longer than NAME_MAX used to be listed and are now skipped.
That sentence is a bit misleading, isn't it? Name length 256..4095: - before: listed, but unusable (ENAMETOOLONG) - now: entry skipped, fetch continues Name length >=4096: - before: aborts the entire fetch (similar to 9p2000.L side) - now: entry skipped, fetch continues But yes, it would be a user-space change nevertheless, so ...
quoted hunk ↗ jump to hunk
Suggested-by: Christian Schoenebeck <linux_oss@crudebyte.com> Link: https://lore.kernel.org/all/3910569.MHq7AAxBmi@weasel/ (local) Signed-off-by: Haobin Wu <redacted> --- fs/9p/vfs_dir.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c index 08d1a3429654..31de9ac913f0 100644 --- a/fs/9p/vfs_dir.c +++ b/fs/9p/vfs_dir.c@@ -119,6 +119,8 @@ static int v9fs_dir_readdir(struct file *file, structdir_context *ctx) rdir->tail = n; } while (rdir->head < rdir->tail) { + size_t namelen; + err = p9stat_read(fid->clnt, rdir->buf + rdir->head, rdir->tail - rdir->head, &st); if (err <= 0) {@@ -126,8 +128,16 @@ static int v9fs_dir_readdir(struct file *file, structdir_context *ctx) return -EIO; } - over = !dir_emit(ctx, st.name, strlen(st.name), - QID2INO(&st.qid), dt_type(&st)); + namelen = strlen(st.name); + if (namelen > NAME_MAX) {
... maybe better if (namelen >= PATH_MAX) here for legacy 9p2000(.u)?
+ p9_debug(P9_DEBUG_ERROR, + "skip dentry: name length %zu > NAME_MAX\n", + namelen); + over = false;
Nit: alternative would be init over = false and dropping explicit assignment inside loop branch here. But that's already personal taste level. /Christian
+ } else {
+ over = !dir_emit(ctx, st.name, namelen,
+ QID2INO(&st.qid), dt_type(&st));
+ }
p9stat_free(&st);
if (over)
return 0;