Messages in this thread Patch in this message | | | Date | Fri, 16 Nov 2012 16:20:16 -0800 | From | Kees Cook <> | Subject | [PATCH] devtmpfs: mount with noexec and nosuid |
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Since devtmpfs is writable, make the default noexec nosuid as well. This protects from the case of a privileged process having an arbitrary file write flaw and an argumentless arbitrary execution (i.e. it would lack the ability to run "mount -o remount,exec,suid /dev"), with a system that already has nosuid,noexec on all other writable mounts.
Cc: ellyjones@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/base/devtmpfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 147d1a4..b7e2e57 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -340,6 +340,7 @@ static int handle_remove(const char *nodename, struct device *dev) int devtmpfs_mount(const char *mntdir) { int err; + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID; if (!mount_dev) return 0; @@ -347,7 +348,7 @@ int devtmpfs_mount(const char *mntdir) if (!thread) return 0; - err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); + err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", mflags, NULL); if (err) printk(KERN_INFO "devtmpfs: error mounting %i\n", err); else @@ -368,11 +369,12 @@ static int handle(const char *name, umode_t mode, struct device *dev) static int devtmpfsd(void *p) { char options[] = "mode=0755"; + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID; int *err = p; *err = sys_unshare(CLONE_NEWNS); if (*err) goto out; - *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); + *err = sys_mount("devtmpfs", "/", "devtmpfs", mflags, options); if (*err) goto out; sys_chdir("/.."); /* will traverse into overmounted root */ -- 1.7.9.5
-- Kees Cook Chrome OS Security
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