We hit hardened usercopy feature check for kernel text access by reading kcore file:
usercopy: kernel memory exposure attempt detected from ffffffff8179a01f (<kernel text>) (4065 bytes) kernel BUG at mm/usercopy.c:75! Bypassing this check for kcore by adding bounce buffer for ktext data. Reported-by: Steve Best <[email protected]> Fixes: f5509cc18daa ("mm: Hardened usercopy") Suggested-by: Kees Cook <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> --- fs/proc/kcore.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index bd3ac9dca252..5c89a07e3d7f 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -509,7 +509,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) if (kern_addr_valid(start)) { unsigned long n; - n = copy_to_user(buffer, (char *)start, tsz); + /* + * Using bounce buffer to bypass the + * hardened user copy kernel text checks. + */ + memcpy(buf, (char *) start, tsz); + n = copy_to_user(buffer, buf, tsz); /* * We cannot distinguish between fault on source * and fault on destination. When this happens -- 2.7.4
