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samples/seccomp: Zero out members based on seccomp_notif_sizes

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The sizes by which seccomp_notif and seccomp_notif_resp are allocated are
based on the SECCOMP_GET_NOTIF_SIZES ioctl. This allows for graceful
extension of these datastructures. If userspace zeroes out the
datastructure based on its version, and it is lagging behind the kernel's
version, it will end up sending trailing garbage. On the other hand,
if it is ahead of the kernel version, it will write extra zero space,
and potentially cause corruption.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Suggested-by: Tycho Andersen <tycho@tycho.ws>
Link: https://lore.kernel.org/r/20191230203503.4925-1-sargun@sargun.me
Fixes: fec7b66905 ("samples: add an example of seccomp user trap")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Sargun Dhillon 2019-12-30 12:35:03 -08:00 committed by Kees Cook
parent fd6988496e
commit 771b894f2f
1 changed files with 2 additions and 2 deletions
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4
samples/seccomp/user-trap.c
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@ -298,14 +298,14 @@ int main(void)
req = malloc(sizes.seccomp_notif);
if (!req)
goto out_close;
memset(req, 0, sizeof(*req));
resp = malloc(sizes.seccomp_notif_resp);
if (!resp)
goto out_req;
memset(resp, 0, sizeof(*resp));
memset(resp, 0, sizes.seccomp_notif_resp);
while (1) {
memset(req, 0, sizes.seccomp_notif);
if (ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, req)) {
perror("ioctl recv");
goto out_resp;