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Thu, 17 Sep 2026 19:49:08 -0700 (PDT) From: Haobin Wu <853555@gmail.com> To: ericvh@kernel.org, lucho@ionkov.net, asmadeus@codewreck.org, v9fs@lists.linux.dev Cc: linux_oss@crudebyte.com, jack@suse.cz, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, aneesh.kumar@linux.vnet.ibm.com, willy@infradead.org, dhowells@redhat.com, viro@zeniv.linux.org.uk, brauner@kernel.org Subject: [PATCH v3 2/3] 9p: skip directory entries with names longer than NAME_MAX Date: Fri, 18 Sep 2026 10:48:50 +0800 Message-ID: <20260918024851.51229-3-853555@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260918024851.51229-1-853555@gmail.com> References: <20260918024851.51229-1-853555@gmail.com> Precedence: bulk X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The 9p wire format carries directory entry names of up to 65535 bytes and nothing on the client checks them against NAME_MAX. Since the previous patch, v9fs_dir_readdir_dotl() passes such names straight to dir_emit(), and the VFS only rejects names of PATH_MAX bytes or more in verify_dirent_name(), as -EIO, which again fails the whole getdents64() call. A name between NAME_MAX and PATH_MAX is therefore returned to userspace even though every later operation on it fails with -ENAMETOOLONG, and POSIX requires readdir() to only return components of at most NAME_MAX bytes. Nothing can use such an entry, so skip it instead of returning it or failing the listing, reusing the strlen() result that was already computed for dir_emit(). Log the skipped entry at P9_DEBUG_ERROR, the same level as the strscpy() failure message this replaces. Suggested-by: Dominique Martinet Link: https://lore.kernel.org/all/vz5bum547fqyxf5z4m3x7tuqkuq52jlopm65t7hvynqeulh7i3@2t4wnhfxs7qv/ Signed-off-by: Haobin Wu <853555@gmail.com> --- fs/9p/vfs_dir.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c index af00b79d801e..08d1a3429654 100644 --- a/fs/9p/vfs_dir.c +++ b/fs/9p/vfs_dir.c @@ -173,6 +173,7 @@ static int v9fs_dir_readdir_dotl(struct file *file, struct dir_context *ctx) } while (rdir->head < rdir->tail) { + size_t namelen; err = p9dirent_read(fid->clnt, rdir->buf + rdir->head, rdir->tail - rdir->head, @@ -182,10 +183,14 @@ static int v9fs_dir_readdir_dotl(struct file *file, struct dir_context *ctx) return -EIO; } - if (!dir_emit(ctx, curdirent.d_name, - strlen(curdirent.d_name), - QID2INO(&curdirent.qid), - curdirent.d_type)) { + namelen = strlen(curdirent.d_name); + if (namelen > NAME_MAX) { + p9_debug(P9_DEBUG_ERROR, + "skip dentry: name length %zu > NAME_MAX\n", + namelen); + } else if (!dir_emit(ctx, curdirent.d_name, namelen, + QID2INO(&curdirent.qid), + curdirent.d_type)) { kfree(curdirent.d_name); return 0; } -- 2.54.0 (Apple Git-157)