From: Greg Kurz Date: Tue, 20 Nov 2018 12:00:35 +0000 (+0100) Subject: 9p: take write lock on fid path updates (CVE-2018-19364) X-Git-Tag: qemu-xen-4.10.4~9 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=fc98458a06c2c7128591fc51e09600a0c81c60cd;p=qemu-xen.git 9p: take write lock on fid path updates (CVE-2018-19364) Recent commit 5b76ef50f62079a 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 Reported-by: zhibin hu Reviewed-by: Prasad J Pandit Signed-off-by: Greg Kurz (cherry picked from commit 5b3c77aa581ebb215125c84b0742119483571e55) --- diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 8e9490c5f5..c3a4f9c385 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -1370,7 +1370,9 @@ 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) { @@ -2139,6 +2141,7 @@ 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); @@ -2179,7 +2182,9 @@ 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; @@ -2195,7 +2200,9 @@ 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); @@ -2213,7 +2220,9 @@ 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; @@ -2251,7 +2260,9 @@ 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); @@ -2262,7 +2273,9 @@ 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); @@ -2273,7 +2286,9 @@ 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);