From 50bb04b7505796a69687946c1712a69043ec1d7d Mon Sep 17 00:00:00 2001 From: Andrew Turner Date: Fri, 27 Sep 2019 16:22:28 +0000 Subject: [PATCH] Check the vfs option length is valid before accessing through When a VFS option passed to nmount is present but NULL the kernel will place an empty option in its internal list. This will have a NULL pointer and a length of 0. When we come to read one of these the kernel will try to load from the last address of virtual memory. This is normally invalid so will fault resulting in a kernel panic. Fix this by checking if the length is valid before dereferencing. MFC after: 3 days Sponsored by: DARPA, AFRL --- sys/kern/vfs_mount.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c index 633fc27a6c98..258b40a69859 100644 --- a/sys/kern/vfs_mount.c +++ b/sys/kern/vfs_mount.c @@ -646,7 +646,7 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct uio *fsoptions) */ fstypelen = 0; error = vfs_getopt(optlist, "fstype", (void **)&fstype, &fstypelen); - if (error || fstype[fstypelen - 1] != '\0') { + if (error || fstypelen <= 0 || fstype[fstypelen - 1] != '\0') { error = EINVAL; if (errmsg != NULL) strncpy(errmsg, "Invalid fstype", errmsg_len); @@ -654,7 +654,7 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct uio *fsoptions) } fspathlen = 0; error = vfs_getopt(optlist, "fspath", (void **)&fspath, &fspathlen); - if (error || fspath[fspathlen - 1] != '\0') { + if (error || fspathlen <= 0 || fspath[fspathlen - 1] != '\0') { error = EINVAL; if (errmsg != NULL) strncpy(errmsg, "Invalid fspath", errmsg_len);