Commit 5b3c77aa authored by Greg Kurz's avatar Greg Kurz
Browse files

9p: take write lock on fid path updates (CVE-2018-19364) 



Recent commit 5b76ef50 fixed a race where v9fs_co_open2() could
possibly overwrite a fid path with v9fs_path_copy() while it is being
accessed by some other thread, ie, use-after-free that can be detected
by ASAN with a custom 9p client.

It turns out that the same can happen at several locations where
v9fs_path_copy() is used to set the fid path. The fix is again to
take the write lock.

Fixes CVE-2018-19364.

Cc: P J P <ppandit@redhat.com>
Reported-by: default avatarzhibin hu <noirfate@gmail.com>
Reviewed-by: default avatarPrasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: default avatarGreg Kurz <groug@kaod.org>
parent 3c035a41

hw/9pfs/9p.c

+15 −0
Original line number Diff line number Diff line
@@ -1391,7 +1391,9 @@ static void coroutine_fn v9fs_walk(void *opaque) 
            err = -EINVAL;

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

    } else {

        newfidp = alloc_fid(s, newfid);

        if (newfidp == NULL) {
@@ -2160,6 +2162,7 @@ static void coroutine_fn v9fs_create(void *opaque) 
    V9fsString extension;

    int iounit;

    V9fsPDU *pdu = opaque;

    V9fsState *s = pdu->s;



    v9fs_path_init(&path);

    v9fs_string_init(&name);
@@ -2200,7 +2203,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
        if (err < 0) {

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

        err = v9fs_co_opendir(pdu, fidp);

        if (err < 0) {

            goto out;
@@ -2216,7 +2221,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
        if (err < 0) {

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

    } else if (perm & P9_STAT_MODE_LINK) {

        int32_t ofid = atoi(extension.data);

        V9fsFidState *ofidp = get_fid(pdu, ofid);
@@ -2234,7 +2241,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
            fidp->fid_type = P9_FID_NONE;

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

        err = v9fs_co_lstat(pdu, &fidp->path, &stbuf);

        if (err < 0) {

            fidp->fid_type = P9_FID_NONE;
@@ -2272,7 +2281,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
        if (err < 0) {

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

    } else if (perm & P9_STAT_MODE_NAMED_PIPE) {

        err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,

                            0, S_IFIFO | (perm & 0777), &stbuf);
@@ -2283,7 +2294,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
        if (err < 0) {

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

    } else if (perm & P9_STAT_MODE_SOCKET) {

        err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,

                            0, S_IFSOCK | (perm & 0777), &stbuf);
@@ -2294,7 +2307,9 @@ static void coroutine_fn v9fs_create(void *opaque) 
        if (err < 0) {

            goto out;

        }

        v9fs_path_write_lock(s);

        v9fs_path_copy(&fidp->path, &path);

        v9fs_path_unlock(s);

    } else {

        err = v9fs_co_open2(pdu, fidp, &name, -1,

                            omode_to_uflags(mode)|O_CREAT, perm, &stbuf);