From 5b3c77aa581ebb215125c84b0742119483571e55 Mon Sep 17 00:00:00 2001 From: Greg Kurz Date: Tue, 20 Nov 2018 13:00:35 +0100 Subject: [PATCH] 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 Upstream-status: Backport Affects: < 3.1.0 CVE: CVE-2018-19364 patch #2 Signed-off-by: Armin Kuster --- hw/9pfs/9p.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index eef289e..267a255 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -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); -- 2.7.4