Messages in this thread | | | From | Daniel Xu <> | Subject | [PATCH bpf v7 0/2] Fix bpf_probe_read_user_str() overcopying | Date | Tue, 17 Nov 2020 12:05:44 -0800 |
| |
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.
v6 -> v7: * Add comments
v5 -> v6: * zero-pad up to sizeof(unsigned long) after NUL
v4 -> v5: * don't read potentially uninitialized memory
v3 -> v4: * directly pass userspace pointer to prog * test more strings of different length
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
kernel/trace/bpf_trace.c | 10 +++ lib/strncpy_from_user.c | 19 ++++- .../bpf/prog_tests/probe_read_user_str.c | 71 +++++++++++++++++++ .../bpf/progs/test_probe_read_user_str.c | 25 +++++++ 4 files changed, 123 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
-- 2.29.2
| |