Description: bpf: fix missing error return in check_stack_boundary()
References:
 http://www.openwall.com/lists/oss-security/2017/12/21/2
Notes:
 carnil> Introduced by f1174f77b50c94eecaa658fdc56fa69b421de4b8 in 4.14-rc1
Bugs:
upstream: released (4.15-rc5) [ea25f914dc164c8d56b36147ecc86bc65f83c469]
4.9-upstream-stable: N/A "Vulnerable code introduced in 4.14-rc1"
3.16-upstream-stable: N/A "Vulnerable code introduced in 4.14-rc1"
3.2-upstream-stable: N/A "Vulnerable code introduced in 4.14-rc1"
sid: released (4.14.7-1) [bugfix/all/bpf-fix-missing-error-return-in-check_stack_boundary.patch]
4.9-stretch-security: N/A "Vulnerable code not present"
3.16-jessie-security: N/A "Vulnerable code not present"
3.2-wheezy-security: N/A "Vulnerable code not present"