From: Zev Weiss <zev@xxxxxxxxxxxxxxxxx> Subject: tools/testing/selftests/sysctl/sysctl.sh: add tests for >32-bit values written to 32-bit integers Patch series "sysctl: fix range-checking in do_proc_dointvec_minmax_conv()", v2. After being left with an unusable system after a typo executing something like 'echo $((1<<24)) > /proc/sys/vm/max_map_count', I found that do_proc_dointvec_minmax_conv() was missing a check to ensure that the converted value actually fits in an int. The first of the following patches enhances the sysctl selftest such that it detects this problem; the second provides a minimal fix (suitable for -stable) such that the selftest passes. The third patch then performs a more thorough refactoring to eliminate the code duplication that led to the bug in the first place (maintaining the passing status of the selftest). This patch (of 3): At present this exposes a bug in do_proc_dointvec_minmax_conv() (it fails to check for values that are too wide to fit in an int). Link: http://lkml.kernel.org/r/20190207123426.9202-2-zev@xxxxxxxxxxxxxxxxx Signed-off-by: Zev Weiss <zev@xxxxxxxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx> Cc: Iurii Zaikin <yzaikin@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- --- a/tools/testing/selftests/sysctl/sysctl.sh~test_sysctl-add-tests-for-32-bit-values-written-to-32-bit-integers +++ a/tools/testing/selftests/sysctl/sysctl.sh @@ -290,6 +290,58 @@ run_numerictests() test_rc } +check_failure() +{ + echo -n "Testing that $1 fails as expected..." + reset_vals + TEST_STR="$1" + orig="$(cat $TARGET)" + echo -n "$TEST_STR" > $TARGET 2> /dev/null + + # write should fail and $TARGET should retain its original value + if [ $? = 0 ] || [ "$(cat $TARGET)" != "$orig" ]; then + echo "FAIL" >&2 + rc=1 + else + echo "ok" + fi + test_rc +} + +run_wideint_tests() +{ + # sysctl conversion functions receive a boolean sign and ulong + # magnitude; here we list the magnitudes we want to test (each of + # which will be tested in both positive and negative forms). Since + # none of these values fit in 32 bits, writing them to an int- or + # uint-typed sysctl should fail. + local magnitudes=( + # common boundary-condition values (zero, +1, -1, INT_MIN, + # and INT_MAX respectively) if truncated to lower 32 bits + # (potential for being falsely deemed in range) + 0x0000000100000000 + 0x0000000100000001 + 0x00000001ffffffff + 0x0000000180000000 + 0x000000017fffffff + + # these look like negatives, but without a leading '-' are + # actually large positives (should be rejected as above + # despite being zero/+1/-1/INT_MIN/INT_MAX in the lower 32) + 0xffffffff00000000 + 0xffffffff00000001 + 0xffffffffffffffff + 0xffffffff80000000 + 0xffffffff7fffffff + ) + + for sign in '' '-'; do + for mag in "${magnitudes[@]}"; do + check_failure "${sign}${mag}" + done + done +} + # Your test must accept digits 3 and 4 to use this run_limit_digit() { @@ -556,6 +608,7 @@ sysctl_test_0001() TEST_STR=$(( $ORIG + 1 )) run_numerictests + run_wideint_tests run_limit_digit } @@ -580,6 +633,7 @@ sysctl_test_0003() TEST_STR=$(( $ORIG + 1 )) run_numerictests + run_wideint_tests run_limit_digit run_limit_digit_int } @@ -592,6 +646,7 @@ sysctl_test_0004() TEST_STR=$(( $ORIG + 1 )) run_numerictests + run_wideint_tests run_limit_digit run_limit_digit_uint } _
