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Thu, 17 Sep 2026 19:49:03 -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 1/3] 9p: skip intermediate directory entry name copy in p9dirent_read() Date: Fri, 18 Sep 2026 10:48:49 +0800 Message-ID: <20260918024851.51229-2-853555@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: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" v9fs_dir_readdir_dotl() decodes each entry of a Rreaddir reply with p9dirent_read(), which parses it through p9pdu_readf("Qqbs"). The 's' conversion in p9pdu_vreadf() already allocates a NUL-terminated copy of the name from the wire buffer; p9dirent_read() then strscpy()s that copy into the fixed 256-byte p9_dirent::d_name and frees the original. The wire format carries the name length in 16 bits, so a name longer than 255 bytes is valid on the wire and may well be valid on the server's filesystem, but it makes strscpy() return -E2BIG. v9fs_dir_readdir_dotl() turns that into -EIO and aborts getdents64(), so every entry after the long one disappears from the listing. Drop the second copy: keep the string allocated by p9pdu_vreadf() in p9_dirent and let v9fs_dir_readdir_dotl(), its only user, free it once dir_emit() has consumed it. p9_dirent is a short-lived stack object, so the string's lifetime does not change. Note that the VFS only rejects names of PATH_MAX bytes or more in verify_dirent_name(), so after this change a name between NAME_MAX and PATH_MAX is returned by getdents64() even though any later lookup on it fails with -ENAMETOOLONG. The next patch skips such entries. Fixes: 7751bdb3a095 ("9p: readdir implementation for 9p2000.L") Closes: https://github.com/microsoft/WSL/issues/41192 Signed-off-by: Haobin Wu <853555@gmail.com> Reviewed-by: Christian Schoenebeck --- fs/9p/vfs_dir.c | 6 +++++- include/net/9p/client.h | 2 +- net/9p/protocol.c | 12 ++---------- 3 files changed, 8 insertions(+), 12 deletions(-) diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c index e0d34e4e9076..af00b79d801e 100644 --- a/fs/9p/vfs_dir.c +++ b/fs/9p/vfs_dir.c @@ -185,8 +185,12 @@ static int v9fs_dir_readdir_dotl(struct file *file, st= ruct dir_context *ctx) if (!dir_emit(ctx, curdirent.d_name, strlen(curdirent.d_name), QID2INO(&curdirent.qid), - curdirent.d_type)) + curdirent.d_type)) { + kfree(curdirent.d_name); return 0; + } + + kfree(curdirent.d_name); =20 ctx->pos =3D curdirent.d_off; rdir->head +=3D err; diff --git a/include/net/9p/client.h b/include/net/9p/client.h index 838a94218b59..9f3079c6f386 100644 --- a/include/net/9p/client.h +++ b/include/net/9p/client.h @@ -268,7 +268,7 @@ struct p9_dirent { struct p9_qid qid; u64 d_off; unsigned char d_type; - char d_name[256]; + char *d_name; }; =20 struct iov_iter; diff --git a/net/9p/protocol.c b/net/9p/protocol.c index 67b0586d807f..d4335884e0c0 100644 --- a/net/9p/protocol.c +++ b/net/9p/protocol.c @@ -770,7 +770,7 @@ int p9dirent_read(struct p9_client *clnt, char *buf, in= t len, { struct p9_fcall fake_pdu; int ret; - char *nameptr; + char *nameptr =3D NULL; =20 fake_pdu.size =3D len; fake_pdu.capacity =3D len; @@ -785,15 +785,7 @@ int p9dirent_read(struct p9_client *clnt, char *buf, i= nt len, return ret; } =20 - ret =3D strscpy(dirent->d_name, nameptr, sizeof(dirent->d_name)); - if (ret < 0) { - p9_debug(P9_DEBUG_ERROR, - "On the wire dirent name too long: %s\n", - nameptr); - kfree(nameptr); - return ret; - } - kfree(nameptr); + dirent->d_name =3D nameptr; =20 return fake_pdu.offset; } --=20 2.54.0 (Apple Git-157) From nobody Fri Sep 25 01:20:08 2026 Received: from mail-pj2-f8.google.com (mail-pj2-f8.google.com [74.125.227.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 905F92749DC for ; 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Thu, 17 Sep 2026 19:49:08 -0700 (PDT) Received: from localhost.localdomain ([38.60.126.44]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33c287b023bsm388217eec.23.2026.09.17.19.49.03 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); 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: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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/vz5bum547fqyxf5z4m3x7tuqkuq52jlopm65t7hvy= nqeulh7i3@2t4wnhfxs7qv/ Signed-off-by: Haobin Wu <853555@gmail.com> Reviewed-by: Christian Schoenebeck --- 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, str= uct dir_context *ctx) } =20 while (rdir->head < rdir->tail) { + size_t namelen; =20 err =3D 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, s= truct dir_context *ctx) return -EIO; } =20 - if (!dir_emit(ctx, curdirent.d_name, - strlen(curdirent.d_name), - QID2INO(&curdirent.qid), - curdirent.d_type)) { + namelen =3D strlen(curdirent.d_name); + if (namelen > NAME_MAX) { + p9_debug(P9_DEBUG_ERROR, + "skip dentry: name length %zu > NAME_MAX\n", + namelen); 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Thu, 17 Sep 2026 19:49:13 -0700 (PDT) Received: from localhost.localdomain ([38.60.126.44]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33c287b023bsm388217eec.23.2026.09.17.19.49.08 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 17 Sep 2026 19:49:12 -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 3/3] 9p: skip over-long directory entry names for legacy 9p2000 too Date: Fri, 18 Sep 2026 10:48:51 +0800 Message-ID: <20260918024851.51229-4-853555@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: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Suggested-by: Christian Schoenebeck Link: https://lore.kernel.org/all/3910569.MHq7AAxBmi@weasel/ Signed-off-by: Haobin Wu <853555@gmail.com> --- 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, struct d= ir_context *ctx) rdir->tail =3D n; } while (rdir->head < rdir->tail) { + size_t namelen; + err =3D p9stat_read(fid->clnt, rdir->buf + rdir->head, rdir->tail - rdir->head, &st); if (err <=3D 0) { @@ -126,8 +128,16 @@ static int v9fs_dir_readdir(struct file *file, struct = dir_context *ctx) return -EIO; } =20 - over =3D !dir_emit(ctx, st.name, strlen(st.name), - QID2INO(&st.qid), dt_type(&st)); + namelen =3D strlen(st.name); + if (namelen > NAME_MAX) { + p9_debug(P9_DEBUG_ERROR, + "skip dentry: name length %zu > NAME_MAX\n", + namelen); + over =3D false; + } else { + over =3D !dir_emit(ctx, st.name, namelen, + QID2INO(&st.qid), dt_type(&st)); + } p9stat_free(&st); if (over) return 0; --=20 2.54.0 (Apple Git-157)