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Blame SOURCES/kvm-virtiofsd-validate-input-buffer-sizes-in-do_write_bu.patch

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From 6877a6c456178d6c1ca9a0ffaabaa7e51105b2ac 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 19:01:22 +0100
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Subject: [PATCH 051/116] virtiofsd: validate input buffer sizes in
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 do_write_buf()
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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: <20200127190227.40942-48-dgilbert@redhat.com>
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Patchwork-id: 93501
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O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 047/112] virtiofsd: validate input buffer sizes in do_write_buf()
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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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There is a small change in behavior: if fuse_write_in->size doesn't
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match the input buffer size then the request is failed.  Previously
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write requests with 1 fuse_buf element would truncate to
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fuse_write_in->size.
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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 0ba8c3c6fce8fe949d59c1fd84d98d220ef9e759)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 tools/virtiofsd/fuse_lowlevel.c | 49 +++++++++++++++++++++++++----------------
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 1 file changed, 30 insertions(+), 19 deletions(-)
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diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
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index 7e10995..611e8b0 100644
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--- a/tools/virtiofsd/fuse_lowlevel.c
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+++ b/tools/virtiofsd/fuse_lowlevel.c
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@@ -1003,8 +1003,8 @@ static void do_write(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
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     }
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 }
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-static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid, const void *inarg,
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-                         struct fuse_bufvec *ibufv)
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+static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid,
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+                         struct fuse_mbuf_iter *iter, struct fuse_bufvec *ibufv)
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 {
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     struct fuse_session *se = req->se;
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     struct fuse_bufvec *pbufv = ibufv;
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@@ -1012,28 +1012,27 @@ static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid, const void *inarg,
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         .buf[0] = ibufv->buf[0],
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         .count = 1,
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     };
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-    struct fuse_write_in *arg = (struct fuse_write_in *)inarg;
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+    struct fuse_write_in *arg;
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+    size_t arg_size = sizeof(*arg);
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     struct fuse_file_info fi;
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     memset(&fi, 0, sizeof(fi));
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+
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+    arg = fuse_mbuf_iter_advance(iter, arg_size);
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+    if (!arg) {
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+        fuse_reply_err(req, EINVAL);
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+        return;
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+    }
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+
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+    fi.lock_owner = arg->lock_owner;
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+    fi.flags = arg->flags;
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     fi.fh = arg->fh;
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     fi.writepage = arg->write_flags & FUSE_WRITE_CACHE;
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     if (ibufv->count == 1) {
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-        fi.lock_owner = arg->lock_owner;
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-        fi.flags = arg->flags;
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-        if (!(tmpbufv.buf[0].flags & FUSE_BUF_IS_FD)) {
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-            tmpbufv.buf[0].mem = PARAM(arg);
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-        }
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-        tmpbufv.buf[0].size -=
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-            sizeof(struct fuse_in_header) + sizeof(struct fuse_write_in);
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-        if (tmpbufv.buf[0].size < arg->size) {
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-            fuse_log(FUSE_LOG_ERR,
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-                     "fuse: do_write_buf: buffer size too small\n");
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-            fuse_reply_err(req, EIO);
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-            return;
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-        }
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-        tmpbufv.buf[0].size = arg->size;
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+        assert(!(tmpbufv.buf[0].flags & FUSE_BUF_IS_FD));
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+        tmpbufv.buf[0].mem = ((char *)arg) + arg_size;
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+        tmpbufv.buf[0].size -= sizeof(struct fuse_in_header) + arg_size;
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         pbufv = &tmpbufv;
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     } else {
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         /*
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@@ -1043,6 +1042,13 @@ static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid, const void *inarg,
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         ibufv->buf[0].size = 0;
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     }
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+    if (fuse_buf_size(pbufv) != arg->size) {
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+        fuse_log(FUSE_LOG_ERR,
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+                 "fuse: do_write_buf: buffer size doesn't match arg->size\n");
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+        fuse_reply_err(req, EIO);
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+        return;
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+    }
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+
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     se->op.write_buf(req, nodeid, pbufv, arg->offset, &fi);
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 }
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@@ -2052,12 +2058,17 @@ void fuse_session_process_buf_int(struct fuse_session *se,
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                                   struct fuse_chan *ch)
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 {
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     const struct fuse_buf *buf = bufv->buf;
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+    struct fuse_mbuf_iter iter = FUSE_MBUF_ITER_INIT(buf);
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     struct fuse_in_header *in;
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     const void *inarg;
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     struct fuse_req *req;
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     int err;
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-    in = buf->mem;
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+    /* The first buffer must be a memory buffer */
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+    assert(!(buf->flags & FUSE_BUF_IS_FD));
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+
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+    in = fuse_mbuf_iter_advance(&iter, sizeof(*in));
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+    assert(in); /* caller guarantees the input buffer is large enough */
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     if (se->debug) {
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         fuse_log(FUSE_LOG_DEBUG,
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@@ -2129,7 +2140,7 @@ void fuse_session_process_buf_int(struct fuse_session *se,
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     inarg = (void *)&in[1];
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     if (in->opcode == FUSE_WRITE && se->op.write_buf) {
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-        do_write_buf(req, in->nodeid, inarg, bufv);
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+        do_write_buf(req, in->nodeid, &iter, bufv);
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     } else {
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         fuse_ll_ops[in->opcode].func(req, in->nodeid, inarg);
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     }
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-- 
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1.8.3.1
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