From: Tycho Andersen Date: Wed, 21 Feb 2018 02:47:46 +0000 (-0700) Subject: ptrace, seccomp: tweak get_metadata behavior slightly X-Git-Tag: v4.16-rc3~9^2~2^2~1 X-Git-Url: http://git.agner.ch/gitweb/?a=commitdiff_plain;h=63bb0045b98ae821e56e27c2250e14bb0ae663e5;p=linux.git ptrace, seccomp: tweak get_metadata behavior slightly Previously if users passed a small size for the input structure size, they would get get odd behavior. It doesn't make sense to pass a structure smaller than at least filter_off size, so let's just give -EINVAL in this case. This changes userspace visible behavior, but was only introduced in commit 26500475ac1b ("ptrace, seccomp: add support for retrieving seccomp metadata") in 4.16-rc2, so should be safe to change if merged before then. Reported-by: Eugene Syromiatnikov Signed-off-by: Tycho Andersen CC: Kees Cook CC: Oleg Nesterov Signed-off-by: Kees Cook --- diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 61bd9dc260c8..1245b2338fff 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -1076,14 +1076,16 @@ long seccomp_get_metadata(struct task_struct *task, size = min_t(unsigned long, size, sizeof(kmd)); - if (copy_from_user(&kmd, data, size)) + if (size < sizeof(kmd.filter_off)) + return -EINVAL; + + if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) return -EFAULT; filter = get_nth_filter(task, kmd.filter_off); if (IS_ERR(filter)) return PTR_ERR(filter); - memset(&kmd, 0, sizeof(kmd)); if (filter->log) kmd.flags |= SECCOMP_FILTER_FLAG_LOG;