From c01578a36ffc8cf17c146537ede0c9a00ac4b077 Mon Sep 17 00:00:00 2001 From: Chandan Rajendra Date: Tue, 19 Mar 2019 15:47:43 +0800 Subject: [PATCH] copy_mount_string: Limit string length to PATH_MAX mainline inclusion from mainline-5.1-rc1 commit fbdb44013202305cd2aefb01df0a92bb55819702 category: bugfix bugzilla: 11150 CVE: NA --------------------------- On ppc64le, When a string with PAGE_SIZE - 1 (i.e. 64k-1) length is passed as a "filesystem type" argument to the mount(2) syscall, copy_mount_string() ends up allocating 64k (the PAGE_SIZE on ppc64le) worth of space for holding the string in kernel's address space. Later, in set_precision() (invoked by get_fs_type() -> __request_module() -> vsnprintf()), we end up assigning strlen(fs-type-string) i.e. 65535 as the value to 'struct printf_spec'->precision member. This field has a width of 16 bits and it is a signed data type. Hence an invalid value ends up getting assigned. This causes the "WARN_ONCE(spec->precision != prec, "precision %d too large", prec)" statement inside set_precision() to be executed. This commit fixes the bug by limiting the length of the string passed by copy_mount_string() to strndup_user() to PATH_MAX. Signed-off-by: Chandan Rajendra Reported-by: Abdul Haleem Suggested-by: Al Viro Signed-off-by: Al Viro Signed-off-by: Yufen Yu Reviewed-by: zhengbin Signed-off-by: Yang Yingliang --- fs/namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/namespace.c b/fs/namespace.c index ee73ca3c8197..629336c91243 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2700,7 +2700,7 @@ void *copy_mount_options(const void __user * data) char *copy_mount_string(const void __user *data) { - return data ? strndup_user(data, PAGE_SIZE) : NULL; + return data ? strndup_user(data, PATH_MAX) : NULL; } /* -- GitLab