bug#26155: Test brief-vs-stat-zero-kernel-lies fails if /proc/cmdline exists but is not readable

[julama]

Package: diffutils
Version: 3.5

Hi

The test tests/brief-vs-stat-zero-kernel-lies fails with

    cat: /proc/cmdline: Permission denied

if /proc/cmdline exists but is not readable. This is for example the case on a Linux kernel with grsecurity patchset and option GRKERNSEC_PROC_USER enabled.

The fix is easy. The script tests/brief-vs-stat-zero-kernel-lies checks in line 13 only for exists (test -f) of $boot (= /proc/cmdline):

    test -f $boot || skip_ no $boot file

making it check for readability (test -r) solves the problem (as the test is now correctly skipped):

    test -r $boot || skip_ file $boot not readable

Kind regards
julama