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linux-user: NETLINK_LIST_MEMBERSHIPS: Allow bad ptr if its length is 0

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getsockopt(fd, SOL_NETLINK, NETLINK_LIST_MEMBERSHIPS, *optval, *optlen)
syscall allows optval to be NULL/invalid if optlen points to a size of
zero. This allows userspace to query the length of the array they should
use to get the full membership list before allocating memory for said
list, then re-calling getsockopt with proper optval/optlen arguments.

Notable users of this pattern include systemd-networkd, which in the
(albeit old) version 237 tested, cannot start without this fix.

Signed-off-by: Frédéric Fortier <frf@ghgsat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210328180135.88449-1-frf@ghgsat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Frédéric Fortier 2021-03-28 14:01:35 -04:00 committed by Laurent Vivier
parent ec2e6e016d
commit 13e340c886
1 changed files with 1 additions and 1 deletions
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2
linux-user/syscall.c
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@ -3025,7 +3025,7 @@ get_timeout:
return -TARGET_EINVAL;
}
results = lock_user(VERIFY_WRITE, optval_addr, len, 1);
if (!results) {
if (!results && len > 0) {
return -TARGET_EFAULT;
}
lv = len;