6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user,
kernel}_str helpers") introduced a subtle bug where
bpf_probe_read_user_str() would potentially copy a few extra bytes after
the NUL terminator.
This issue is particularly nefarious when strings are used as map keys,
as seemingly identical strings can occupy multiple entries in a map.
This patchset fixes the issue and introduces a selftest to prevent
future regressions.
v2 -> v3:
* set pid filter before attaching prog in selftest
* use long instead of int as bpf_probe_read_user_str() retval
* style changes
v1 -> v2:
* add Fixes: tag
* add selftest
Daniel Xu (2):
lib/strncpy_from_user.c: Don't overcopy bytes after NUL terminator
selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes
after NUL
lib/strncpy_from_user.c | 9 ++-
.../bpf/prog_tests/probe_read_user_str.c | 60 +++++++++++++++++++
.../bpf/progs/test_probe_read_user_str.c | 34 +++++++++++
3 files changed, 101 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c
create mode 100644 tools/testing/selftests/bpf/progs/test_probe_read_user_str.c
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2.28.0
