[PATCH 0/6] lib: Add safe string funtions

From: Tobin C. Harding
Date: Mon Feb 18 2019 - 18:24:20 EST

No file maintainer, CC'ing all those who touched this file :) And
Shua for kselftest stuff.

Hi Kess,

During your talk at LCA you mentioned that we could do with a couple
more safe string functions. One to zero the tail of the destination
buffer after call to strscpy() and also the self explanatory

Here is a patch set with my attempts to implement these two functions.

While doing this I noticed that we have a test module for lib/string.c
(lib/test_string.c) that is not tied into kselftest. So I enable this
first up in patch 1.

Patch 2 and 3 are function docstring cleanups.

Patch 4 adds the copy and zero function, naming it strscpy_zeroed().
I'd love some help naming this better. Patch also adds test code.

Patch 5 fixes function docstring to correctly document the behavior of

Patch 6 adds strscpy_from_user(). Does not include test code.

I had to do a bit of learning for getting the tests hooked into
kselftest, I think its all correct. Module is built correctly when the
config option is present and the tests run both via

make -C tools/testing/selftests TARGETS=lib run_tests

and via loading the module manually. As a side note, this series leaves
tools/testing/selftests/lib with 4 shell scripts that are identical
except the test name. We could probably do with refactoring them into a
single script.

Patchset introduces a checkpatch warning

WARNING:CONFIG_DESCRIPTION: please write a paragraph that describes the config symbol fully

I couldn't work out if this is a false positive or not? Does the new
config option CONFIG_TEST_STRING need more documentation? I don't see
where extra docs should be added and it seems self explanatory as is.


Tobin C. Harding (6):
lib/string: Enable string selftesting
lib/string: Fix erroneous 'overflow' documentation
lib/string: Use correct docstring format
lib/string: Add string copy/zero function
lib: Fix function documentation for strncpy_from_user
lib: Add function strscpy_from_user()

include/linux/string.h | 4 ++
lib/Kconfig.debug | 14 +++++++
lib/Makefile | 2 +-
lib/string.c | 41 ++++++++++++++----
lib/strncpy_from_user.c | 60 ++++++++++++++++++++++-----
lib/test_string.c | 35 +++++++++++++++-
tools/testing/selftests/lib/Makefile | 2 +-
tools/testing/selftests/lib/config | 1 +
tools/testing/selftests/lib/string.sh | 19 +++++++++
9 files changed, 157 insertions(+), 21 deletions(-)
create mode 100755 tools/testing/selftests/lib/string.sh