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ptrace, seccomp: tweak get_metadata behavior slightly

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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
26500475ac ("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 <esyr@redhat.com>
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Tycho Andersen 2018-02-20 19:47:46 -07:00 committed by Kees Cook
parent 2a040f9f39
commit 63bb0045b9
1 changed files with 4 additions and 2 deletions
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6
kernel/seccomp.c
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@ -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;