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From 97e232e75bbc0032f4a309d248f383384612eafe Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Mon, 27 Jan 2020 19:01:25 +0100
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Subject: [PATCH 054/116] virtiofsd: prevent ".." escape in lo_do_readdir()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20200127190227.40942-51-dgilbert@redhat.com>
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Patchwork-id: 93507
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O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 050/112] virtiofsd: prevent ".." escape in lo_do_readdir()
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Bugzilla: 1694164
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Construct a fake dirent for the root directory's ".." entry.  This hides
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the parent directory from the FUSE client.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Sergio Lopez <slp@redhat.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit 752272da2b68a2312f0e11fc5303015a6c3ee1ac)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 tools/virtiofsd/passthrough_ll.c | 36 ++++++++++++++++++++++--------------
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 1 file changed, 22 insertions(+), 14 deletions(-)
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diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
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index 79d5966..e3d65c3 100644
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--- a/tools/virtiofsd/passthrough_ll.c
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+++ b/tools/virtiofsd/passthrough_ll.c
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@@ -1149,19 +1149,25 @@ out_err:
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 static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
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                           off_t offset, struct fuse_file_info *fi, int plus)
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 {
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+    struct lo_data *lo = lo_data(req);
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     struct lo_dirp *d;
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+    struct lo_inode *dinode;
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     char *buf = NULL;
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     char *p;
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     size_t rem = size;
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-    int err = ENOMEM;
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+    int err = EBADF;
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-    (void)ino;
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+    dinode = lo_inode(req, ino);
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+    if (!dinode) {
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+        goto error;
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+    }
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     d = lo_dirp(req, fi);
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     if (!d) {
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         goto error;
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     }
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+    err = ENOMEM;
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     buf = calloc(1, size);
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     if (!buf) {
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         goto error;
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@@ -1192,15 +1198,21 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
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         }
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         nextoff = d->entry->d_off;
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         name = d->entry->d_name;
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+
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         fuse_ino_t entry_ino = 0;
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+        struct fuse_entry_param e = (struct fuse_entry_param){
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+            .attr.st_ino = d->entry->d_ino,
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+            .attr.st_mode = d->entry->d_type << 12,
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+        };
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+
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+        /* Hide root's parent directory */
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+        if (dinode == &lo->root && strcmp(name, "..") == 0) {
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+            e.attr.st_ino = lo->root.ino;
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+            e.attr.st_mode = DT_DIR << 12;
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+        }
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+
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         if (plus) {
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-            struct fuse_entry_param e;
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-            if (is_dot_or_dotdot(name)) {
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-                e = (struct fuse_entry_param){
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-                    .attr.st_ino = d->entry->d_ino,
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-                    .attr.st_mode = d->entry->d_type << 12,
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-                };
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-            } else {
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+            if (!is_dot_or_dotdot(name)) {
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                 err = lo_do_lookup(req, ino, name, &e);
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                 if (err) {
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                     goto error;
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@@ -1210,11 +1222,7 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
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             entsize = fuse_add_direntry_plus(req, p, rem, name, &e, nextoff);
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         } else {
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-            struct stat st = {
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-                .st_ino = d->entry->d_ino,
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-                .st_mode = d->entry->d_type << 12,
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-            };
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-            entsize = fuse_add_direntry(req, p, rem, name, &st, nextoff);
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+            entsize = fuse_add_direntry(req, p, rem, name, &e.attr, nextoff);
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         }
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         if (entsize > rem) {
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             if (entry_ino != 0) {
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-- 
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1.8.3.1
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