From 9de30f3f7f4d31037cfbb7c787e1089c1944b3a7 Mon Sep 17 00:00:00 2001 From: Tycho Andersen Date: Fri, 2 Nov 2018 14:18:22 -0600 Subject: dlm: don't leak kernel pointer to userspace In copy_result_to_user(), we first create a struct dlm_lock_result, which contains a struct dlm_lksb, the last member of which is a pointer to the lvb. Unfortunately, we copy the entire struct dlm_lksb to the result struct, which is then copied to userspace at the end of the function, leaking the contents of sb_lvbptr, which is a valid kernel pointer in some cases (indeed, later in the same function the data it points to is copied to userspace). It is an error to leak kernel pointers to userspace, as it undermines KASLR protections (see e.g. 65eea8edc31 ("floppy: Do not copy a kernel pointer to user memory in FDGETPRM ioctl") for another example of this). Signed-off-by: Tycho Andersen Signed-off-by: David Teigland --- fs/dlm/user.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/dlm') diff --git a/fs/dlm/user.c b/fs/dlm/user.c index 2a669390cd7f..13f29409600b 100644 --- a/fs/dlm/user.c +++ b/fs/dlm/user.c @@ -702,7 +702,7 @@ static int copy_result_to_user(struct dlm_user_args *ua, int compat, result.version[0] = DLM_DEVICE_VERSION_MAJOR; result.version[1] = DLM_DEVICE_VERSION_MINOR; result.version[2] = DLM_DEVICE_VERSION_PATCH; - memcpy(&result.lksb, &ua->lksb, sizeof(struct dlm_lksb)); + memcpy(&result.lksb, &ua->lksb, offsetof(struct dlm_lksb, sb_lvbptr)); result.user_lksb = ua->user_lksb; /* FIXME: dlm1 provides for the user's bastparam/addr to not be updated -- cgit v1.2.3-70-g09d2