From 8d00d6c88774482d4dc08383c58db01472946508 Mon Sep 17 00:00:00 2001 From: Andrew Turner Date: Fri, 4 Oct 2019 14:10:56 +0000 Subject: [PATCH] MFS r353032: 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. Approved by: re (kib) 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 c471bf73046..2ed6b5951e4 100644 --- a/sys/kern/vfs_mount.c +++ b/sys/kern/vfs_mount.c @@ -603,7 +603,7 @@ 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); @@ -611,7 +611,7 @@ 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); -- 2.45.0