On Sun, Sep 06, 2026 at 09:51:34PM -0400, Aaron Tomlin wrote:
> When pretty-printing augmented syscall arguments in perf trace, raw payload
> data captured from BPF programs is passed to various argument formatters
> via struct syscall_arg.
>
> However, when processing malformed, truncated, or untrusted perf.data
> records (e.g., truncated reads in BPF ringbuffers, cross-architecture
> replays, or crafted sample records), the payload can be shorter than
> expected or contain invalid size fields:
> 1. Dereferencing augmented_arg fields before validating that
> arg->augmented.size is at least sizeof(struct augmented_arg) can read
> past the available buffer.
>
> 2. Passing augmented_arg->size to formatters or loop counters without
> bounding it against the remaining buffer can cause out-of-bounds memory
> reads.
>
> 3. In multi-argument syscalls, calculating consumed bytes as:
>
> consumed = sizeof(*augmented_arg) + augmented_arg->size;
>
> without bounds checking can overflow signed integer bounds or cause
> arg->augmented.size to underflow. This advances arg->augmented.args
> out of bounds, corrupting parsing state for all subsequent
> arguments in the same syscall.
>
> 4. Type/family-specific beautifiers (i.e., BTF struct dump, sockaddr,
> timespec, perf_event_attr) can dereference structure fields without
> verifying that the payload contains sufficient bytes for the target
> type.
>
> This series adds comprehensive upper-bound and payload-size checks across
> all augmented argument beautifiers in perf trace. If validation fails in
> any beautifier, it cleanly falls back to printing the raw pointer/hex
> value.
>
> To facilitate clean, conflict-free backports across active LTS kernels,
> each formatter fix is isolated to its own commit.
>
> Changes since v1:
>
> - Expanded the original single patch into a 6-patch series in response to
> reviewer feedback from sashiko-bot regarding similar bounds check
> omissions across other augmented formatters in perf trace
>
> - Added new patch validating payload bounds and consumed offset
> calculations in syscall_arg__scnprintf_augmented_string()
>
> - Added new patch validating payload bounds before byte traversal in
> syscall_arg__scnprintf_buf(), isolated to ensure an independent Fixes:
> tag for stable backports
>
> - Added new patch validating payload size against sizeof(struct timespec)
> in syscall_arg__scnprintf_augmented_timespec()
>
> - Added new patch validating payload bounds and family-specific lengths in
> syscall_arg__scnprintf_augmented_sockaddr()
>
> - Added new patch validating payload size against at least
> PERF_ATTR_SIZE_VER0 in
> syscall_arg__scnprintf_augmented_perf_event_attr()
>
> - Link to v1: https://lore.kernel.org/all/20260906011132.279321-1-atomlin@atomlin.com/
>
> Aaron Tomlin (6):
> perf trace: Add upper bound checks for augmented BTF struct printing
> perf trace: Validate payload bounds in augmented string beautifier
> perf trace: Validate payload bounds in augmented buffer beautifier
> perf trace beauty: Validate payload size in augmented timespec
> beautifier
> perf trace beauty: Validate payload size in augmented sockaddr
> beautifier
> perf trace beauty: Validate payload size in augmented perf_event_open
> beautifier
>
> tools/perf/builtin-trace.c | 36 +++++++++++++++++------
> tools/perf/trace/beauty/perf_event_open.c | 19 ++++++++++--
> tools/perf/trace/beauty/sockaddr.c | 35 ++++++++++++++++++----
> tools/perf/trace/beauty/timespec.c | 19 ++++++++++--
> 4 files changed, 89 insertions(+), 20 deletions(-)
>
>
> base-commit: 02f6847e1822714a4201b87e42f92b0d43e8549d
> --
> 2.55.0
>
Kindly disregard this iteration, as per Sashiko [1].
The observations regarding uninitialised augmented_arg->size reads, arising
from the fact that several eBPF probes in augmented_raw_syscalls.bpf.c omit
populating this field from the reused per-CPU map, are indeed entirely
valid.
Likewise, the points concerning dispatch extensibility and variable-length
path handling in the sockaddr beautifier, alongside potential TOCTOU
discrepancies in perf_event_open, have been taken on board. Additionally,
regarding the suggested inclusion of <stdbool.h> and <stddef.h> in
sockaddr.c, these have been intentionally omitted as the requisite types
and macros (bool and offsetof()) are already provided unconditionally via
trace/beauty/beauty.h.
[1]: https://sashiko.dev/#/patchset/20260907015140.363076-1-atomlin%40atomlin.com
--
Aaron Tomlin