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9p: skip over-long directory entry names for legacy 9p2000 too

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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,
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

Suggested-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Link: https://lore.kernel.org/all/3910569.MHq7AAxBmi@weasel/
Signed-off-by: Haobin Wu <853555@gmail.com>
Message-ID: <20260918024851.51229-4-853555@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
Haobin Wu 2026-09-18 10:48:51 +08:00 committed by Dominique Martinet
parent edd807dc20
commit 55d6732b80
1 changed files with 12 additions and 3 deletions
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15
fs/9p/vfs_dir.c
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@ -85,7 +85,6 @@ static struct p9_rdir *v9fs_alloc_rdir_buf(struct file *filp, int buflen)
static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
{
bool over;
struct p9_wstat st;
int err = 0;
struct p9_fid *fid;
@ -125,6 +124,9 @@ static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
rdir->offset = ctx->pos;
}
while (rdir->head < rdir->tail) {
bool over = false;
size_t namelen;
err = p9stat_read(fid->clnt, rdir->buf + rdir->head,
rdir->tail - rdir->head, &st);
if (err <= 0) {
@ -132,8 +134,15 @@ static int v9fs_dir_readdir(struct file *file, struct dir_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) {
p9_debug(P9_DEBUG_ERROR,
"skip dentry: name length %zu > NAME_MAX\n",
namelen);
} else {
over = !dir_emit(ctx, st.name, namelen,
QID2INO(&st.qid), dt_type(&st));
}
p9stat_free(&st);
if (over)
return 0;