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qemu: Fix CVE-2020-35517

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CVE:
CVE-2020-35517

(From OE-Core rev: 51376edb13eed748395ebe1e56081c092565be9b)

Signed-off-by: Khairul Rohaizzat Jamaluddin <khairul.rohaizzat.jamaluddin@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Khairul Rohaizzat Jamaluddin
2021-04-07 05:42:35 +00:00
committed by Richard Purdie
parent 84a6d97670
commit b50e51b1c8
4 changed files with 576 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
meta/recipes-devtools/qemu/qemu.inc
View File

@@ -31,6 +31,9 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
file://determinism.patch \
file://0001-tests-meson.build-use-relative-path-to-refer-to-file.patch \
file://CVE-2021-20203.patch \
file://CVE-2020-35517_1.patch \
file://CVE-2020-35517_2.patch \
file://CVE-2020-35517_3.patch \
"
UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"

153
meta/recipes-devtools/qemu/qemu/CVE-2020-35517_1.patch Normal file
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@@ -0,0 +1,153 @@
From 8afaaee976965b7fb90ec225a51d60f35c5f173c Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 4 Feb 2021 15:02:06 +0000
Subject: [PATCH] virtiofsd: extract lo_do_open() from lo_open()
Both lo_open() and lo_create() have similar code to open a file. Extract
a common lo_do_open() function from lo_open() that will be used by
lo_create() in a later commit.
Since lo_do_open() does not otherwise need fuse_req_t req, convert
lo_add_fd_mapping() to use struct lo_data *lo instead.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210204150208.367837-2-stefanha@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Upstream-Status: Backport
[https://github.com/qemu/qemu/commit/8afaaee976965b7fb90ec225a51d60f35c5f173c]
CVE: CVE-2020-35517
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Khairul Rohaizzat Jamaluddin <khairul.rohaizzat.jamaluddin@intel.com>
---
tools/virtiofsd/passthrough_ll.c | 73 +++++++++++++++++++++++++---------------
1 file changed, 46 insertions(+), 27 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 5fb36d9..f14fa51 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -459,17 +459,17 @@ static void lo_map_remove(struct lo_map *map, size_t key)
}
/* Assumes lo->mutex is held */
-static ssize_t lo_add_fd_mapping(fuse_req_t req, int fd)
+static ssize_t lo_add_fd_mapping(struct lo_data *lo, int fd)
{
struct lo_map_elem *elem;
- elem = lo_map_alloc_elem(&lo_data(req)->fd_map);
+ elem = lo_map_alloc_elem(&lo->fd_map);
if (!elem) {
return -1;
}
elem->fd = fd;
- return elem - lo_data(req)->fd_map.elems;
+ return elem - lo->fd_map.elems;
}
/* Assumes lo->mutex is held */
@@ -1651,6 +1651,38 @@ static void update_open_flags(int writeback, int allow_direct_io,
}
}
+static int lo_do_open(struct lo_data *lo, struct lo_inode *inode,
+ struct fuse_file_info *fi)
+{
+ char buf[64];
+ ssize_t fh;
+ int fd;
+
+ update_open_flags(lo->writeback, lo->allow_direct_io, fi);
+
+ sprintf(buf, "%i", inode->fd);
+ fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
+ if (fd == -1) {
+ return errno;
+ }
+
+ pthread_mutex_lock(&lo->mutex);
+ fh = lo_add_fd_mapping(lo, fd);
+ pthread_mutex_unlock(&lo->mutex);
+ if (fh == -1) {
+ close(fd);
+ return ENOMEM;
+ }
+
+ fi->fh = fh;
+ if (lo->cache == CACHE_NONE) {
+ fi->direct_io = 1;
+ } else if (lo->cache == CACHE_ALWAYS) {
+ fi->keep_cache = 1;
+ }
+ return 0;
+}
+
static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, struct fuse_file_info *fi)
{
@@ -1691,7 +1723,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
ssize_t fh;
pthread_mutex_lock(&lo->mutex);
- fh = lo_add_fd_mapping(req, fd);
+ fh = lo_add_fd_mapping(lo, fd);
pthread_mutex_unlock(&lo->mutex);
if (fh == -1) {
close(fd);
@@ -1892,38 +1924,25 @@ static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,
static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
{
- int fd;
- ssize_t fh;
- char buf[64];
struct lo_data *lo = lo_data(req);
+ struct lo_inode *inode = lo_inode(req, ino);
+ int err;
fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=%" PRIu64 ", flags=%d)\n", ino,
fi->flags);
- update_open_flags(lo->writeback, lo->allow_direct_io, fi);
-
- sprintf(buf, "%i", lo_fd(req, ino));
- fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
- if (fd == -1) {
- return (void)fuse_reply_err(req, errno);
- }
-
- pthread_mutex_lock(&lo->mutex);
- fh = lo_add_fd_mapping(req, fd);
- pthread_mutex_unlock(&lo->mutex);
- if (fh == -1) {
- close(fd);
- fuse_reply_err(req, ENOMEM);
+ if (!inode) {
+ fuse_reply_err(req, EBADF);
return;
}
- fi->fh = fh;
- if (lo->cache == CACHE_NONE) {
- fi->direct_io = 1;
- } else if (lo->cache == CACHE_ALWAYS) {
- fi->keep_cache = 1;
+ err = lo_do_open(lo, inode, fi);
+ lo_inode_put(lo, &inode);
+ if (err) {
+ fuse_reply_err(req, err);
+ } else {
+ fuse_reply_open(req, fi);
}
- fuse_reply_open(req, fi);
}
static void lo_release(fuse_req_t req, fuse_ino_t ino,
--
1.8.3.1

117
meta/recipes-devtools/qemu/qemu/CVE-2020-35517_2.patch Normal file
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@@ -0,0 +1,117 @@
From 22d2ece71e533310da31f2857ebc4a00d91968b3 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 4 Feb 2021 15:02:07 +0000
Subject: [PATCH] virtiofsd: optionally return inode pointer from
lo_do_lookup()
lo_do_lookup() finds an existing inode or allocates a new one. It
increments nlookup so that the inode stays alive until the client
releases it.
Existing callers don't need the struct lo_inode so the function doesn't
return it. Extend the function to optionally return the inode. The next
commit will need it.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20210204150208.367837-3-stefanha@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Upstream-Status: Backport
[https://github.com/qemu/qemu/commit/22d2ece71e533310da31f2857ebc4a00d91968b3]
CVE: CVE-2020-35517
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Khairul Rohaizzat Jamaluddin <khairul.rohaizzat.jamaluddin@intel.com>
---
tools/virtiofsd/passthrough_ll.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index f14fa51..aa35fc6 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -831,11 +831,13 @@ static int do_statx(struct lo_data *lo, int dirfd, const char *pathname,
}
/*
- * Increments nlookup and caller must release refcount using
- * lo_inode_put(&parent).
+ * Increments nlookup on the inode on success. unref_inode_lolocked() must be
+ * called eventually to decrement nlookup again. If inodep is non-NULL, the
+ * inode pointer is stored and the caller must call lo_inode_put().
*/
static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
- struct fuse_entry_param *e)
+ struct fuse_entry_param *e,
+ struct lo_inode **inodep)
{
int newfd;
int res;
@@ -845,6 +847,10 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
struct lo_inode *inode = NULL;
struct lo_inode *dir = lo_inode(req, parent);
+ if (inodep) {
+ *inodep = NULL;
+ }
+
/*
* name_to_handle_at() and open_by_handle_at() can reach here with fuse
* mount point in guest, but we don't have its inode info in the
@@ -913,7 +919,14 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
pthread_mutex_unlock(&lo->mutex);
}
e->ino = inode->fuse_ino;
- lo_inode_put(lo, &inode);
+
+ /* Transfer ownership of inode pointer to caller or drop it */
+ if (inodep) {
+ *inodep = inode;
+ } else {
+ lo_inode_put(lo, &inode);
+ }
+
lo_inode_put(lo, &dir);
fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent,
@@ -948,7 +961,7 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
return;
}
- err = lo_do_lookup(req, parent, name, &e);
+ err = lo_do_lookup(req, parent, name, &e, NULL);
if (err) {
fuse_reply_err(req, err);
} else {
@@ -1056,7 +1069,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
goto out;
}
- saverr = lo_do_lookup(req, parent, name, &e);
+ saverr = lo_do_lookup(req, parent, name, &e, NULL);
if (saverr) {
goto out;
}
@@ -1534,7 +1547,7 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
if (plus) {
if (!is_dot_or_dotdot(name)) {
- err = lo_do_lookup(req, ino, name, &e);
+ err = lo_do_lookup(req, ino, name, &e, NULL);
if (err) {
goto error;
}
@@ -1732,7 +1745,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
}
fi->fh = fh;
- err = lo_do_lookup(req, parent, name, &e);
+ err = lo_do_lookup(req, parent, name, &e, NULL);
}
if (lo->cache == CACHE_NONE) {
fi->direct_io = 1;
--
1.8.3.1

303
meta/recipes-devtools/qemu/qemu/CVE-2020-35517_3.patch Normal file
View File

@@ -0,0 +1,303 @@
From a3fdbbc7f271bff7d53d0501b29d910ece0b3789 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 4 Feb 2021 15:02:08 +0000
Subject: [PATCH] virtiofsd: prevent opening of special files (CVE-2020-35517)
A well-behaved FUSE client does not attempt to open special files with
FUSE_OPEN because they are handled on the client side (e.g. device nodes
are handled by client-side device drivers).
The check to prevent virtiofsd from opening special files is missing in
a few cases, most notably FUSE_OPEN. A malicious client can cause
virtiofsd to open a device node, potentially allowing the guest to
escape. This can be exploited by a modified guest device driver. It is
not exploitable from guest userspace since the guest kernel will handle
special files inside the guest instead of sending FUSE requests.
This patch fixes this issue by introducing the lo_inode_open() function
to check the file type before opening it. This is a short-term solution
because it does not prevent a compromised virtiofsd process from opening
device nodes on the host.
Restructure lo_create() to try O_CREAT | O_EXCL first. Note that O_CREAT
| O_EXCL does not follow symlinks, so O_NOFOLLOW masking is not
necessary here. If the file exists and the user did not specify O_EXCL,
open it via lo_do_open().
Reported-by: Alex Xu <alex@alxu.ca>
Fixes: CVE-2020-35517
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210204150208.367837-4-stefanha@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Upstream-Status: Backport
[https://github.com/qemu/qemu/commit/a3fdbbc7f271bff7d53d0501b29d910ece0b3789]
CVE: CVE-2020-35517
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Khairul Rohaizzat Jamaluddin <khairul.rohaizzat.jamaluddin@intel.com>
---
tools/virtiofsd/passthrough_ll.c | 144 ++++++++++++++++++++-----------
1 file changed, 92 insertions(+), 52 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index aa35fc6ba5a5..147b59338a18 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -555,6 +555,38 @@ static int lo_fd(fuse_req_t req, fuse_ino_t ino)
return fd;
}
+/*
+ * Open a file descriptor for an inode. Returns -EBADF if the inode is not a
+ * regular file or a directory.
+ *
+ * Use this helper function instead of raw openat(2) to prevent security issues
+ * when a malicious client opens special files such as block device nodes.
+ * Symlink inodes are also rejected since symlinks must already have been
+ * traversed on the client side.
+ */
+static int lo_inode_open(struct lo_data *lo, struct lo_inode *inode,
+ int open_flags)
+{
+ g_autofree char *fd_str = g_strdup_printf("%d", inode->fd);
+ int fd;
+
+ if (!S_ISREG(inode->filetype) && !S_ISDIR(inode->filetype)) {
+ return -EBADF;
+ }
+
+ /*
+ * The file is a symlink so O_NOFOLLOW must be ignored. We checked earlier
+ * that the inode is not a special file but if an external process races
+ * with us then symlinks are traversed here. It is not possible to escape
+ * the shared directory since it is mounted as "/" though.
+ */
+ fd = openat(lo->proc_self_fd, fd_str, open_flags & ~O_NOFOLLOW);
+ if (fd < 0) {
+ return -errno;
+ }
+ return fd;
+}
+
static void lo_init(void *userdata, struct fuse_conn_info *conn)
{
struct lo_data *lo = (struct lo_data *)userdata;
@@ -684,9 +716,9 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
if (fi) {
truncfd = fd;
} else {
- sprintf(procname, "%i", ifd);
- truncfd = openat(lo->proc_self_fd, procname, O_RDWR);
+ truncfd = lo_inode_open(lo, inode, O_RDWR);
if (truncfd < 0) {
+ errno = -truncfd;
goto out_err;
}
}
@@ -848,7 +880,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
struct lo_inode *dir = lo_inode(req, parent);
if (inodep) {
- *inodep = NULL;
+ *inodep = NULL; /* in case there is an error */
}
/*
@@ -1664,19 +1696,26 @@ static void update_open_flags(int writeback, int allow_direct_io,
}
}
+/*
+ * Open a regular file, set up an fd mapping, and fill out the struct
+ * fuse_file_info for it. If existing_fd is not negative, use that fd instead
+ * opening a new one. Takes ownership of existing_fd.
+ *
+ * Returns 0 on success or a positive errno.
+ */
static int lo_do_open(struct lo_data *lo, struct lo_inode *inode,
- struct fuse_file_info *fi)
+ int existing_fd, struct fuse_file_info *fi)
{
- char buf[64];
ssize_t fh;
- int fd;
+ int fd = existing_fd;
update_open_flags(lo->writeback, lo->allow_direct_io, fi);
- sprintf(buf, "%i", inode->fd);
- fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
- if (fd == -1) {
- return errno;
+ if (fd < 0) {
+ fd = lo_inode_open(lo, inode, fi->flags);
+ if (fd < 0) {
+ return -fd;
+ }
}
pthread_mutex_lock(&lo->mutex);
@@ -1699,9 +1738,10 @@ static int lo_do_open(struct lo_data *lo, struct lo_inode *inode,
static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, struct fuse_file_info *fi)
{
- int fd;
+ int fd = -1;
struct lo_data *lo = lo_data(req);
struct lo_inode *parent_inode;
+ struct lo_inode *inode = NULL;
struct fuse_entry_param e;
int err;
struct lo_cred old = {};
@@ -1727,36 +1767,38 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
update_open_flags(lo->writeback, lo->allow_direct_io, fi);
- fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
- mode);
+ /* Try to create a new file but don't open existing files */
+ fd = openat(parent_inode->fd, name, fi->flags | O_CREAT | O_EXCL, mode);
err = fd == -1 ? errno : 0;
- lo_restore_cred(&old);
- if (!err) {
- ssize_t fh;
+ lo_restore_cred(&old);
- pthread_mutex_lock(&lo->mutex);
- fh = lo_add_fd_mapping(lo, fd);
- pthread_mutex_unlock(&lo->mutex);
- if (fh == -1) {
- close(fd);
- err = ENOMEM;
- goto out;
- }
+ /* Ignore the error if file exists and O_EXCL was not given */
+ if (err && (err != EEXIST || (fi->flags & O_EXCL))) {
+ goto out;
+ }
- fi->fh = fh;
- err = lo_do_lookup(req, parent, name, &e, NULL);
+ err = lo_do_lookup(req, parent, name, &e, &inode);
+ if (err) {
+ goto out;
}
- if (lo->cache == CACHE_NONE) {
- fi->direct_io = 1;
- } else if (lo->cache == CACHE_ALWAYS) {
- fi->keep_cache = 1;
+
+ err = lo_do_open(lo, inode, fd, fi);
+ fd = -1; /* lo_do_open() takes ownership of fd */
+ if (err) {
+ /* Undo lo_do_lookup() nlookup ref */
+ unref_inode_lolocked(lo, inode, 1);
}
out:
+ lo_inode_put(lo, &inode);
lo_inode_put(lo, &parent_inode);
if (err) {
+ if (fd >= 0) {
+ close(fd);
+ }
+
fuse_reply_err(req, err);
} else {
fuse_reply_create(req, &e, fi);
@@ -1770,7 +1812,6 @@ static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo,
pid_t pid, int *err)
{
struct lo_inode_plock *plock;
- char procname[64];
int fd;
plock =
@@ -1787,12 +1828,10 @@ static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo,
}
/* Open another instance of file which can be used for ofd locks. */
- sprintf(procname, "%i", inode->fd);
-
/* TODO: What if file is not writable? */
- fd = openat(lo->proc_self_fd, procname, O_RDWR);
- if (fd == -1) {
- *err = errno;
+ fd = lo_inode_open(lo, inode, O_RDWR);
+ if (fd < 0) {
+ *err = -fd;
free(plock);
return NULL;
}
@@ -1949,7 +1988,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
return;
}
- err = lo_do_open(lo, inode, fi);
+ err = lo_do_open(lo, inode, -1, fi);
lo_inode_put(lo, &inode);
if (err) {
fuse_reply_err(req, err);
@@ -2014,39 +2053,40 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi)
{
+ struct lo_inode *inode = lo_inode(req, ino);
+ struct lo_data *lo = lo_data(req);
int res;
int fd;
- char *buf;
fuse_log(FUSE_LOG_DEBUG, "lo_fsync(ino=%" PRIu64 ", fi=0x%p)\n", ino,
(void *)fi);
- if (!fi) {
- struct lo_data *lo = lo_data(req);
-
- res = asprintf(&buf, "%i", lo_fd(req, ino));
- if (res == -1) {
- return (void)fuse_reply_err(req, errno);
- }
+ if (!inode) {
+ fuse_reply_err(req, EBADF);
+ return;
+ }
- fd = openat(lo->proc_self_fd, buf, O_RDWR);
- free(buf);
- if (fd == -1) {
- return (void)fuse_reply_err(req, errno);
+ if (!fi) {
+ fd = lo_inode_open(lo, inode, O_RDWR);
+ if (fd < 0) {
+ res = -fd;
+ goto out;
}
} else {
fd = lo_fi_fd(req, fi);
}
if (datasync) {
- res = fdatasync(fd);
+ res = fdatasync(fd) == -1 ? errno : 0;
} else {
- res = fsync(fd);
+ res = fsync(fd) == -1 ? errno : 0;
}
if (!fi) {
close(fd);
}
- fuse_reply_err(req, res == -1 ? errno : 0);
+out:
+ lo_inode_put(lo, &inode);
+ fuse_reply_err(req, res);
}
static void lo_read(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset,