[PATCH v2 perf-tools-next 1/6] perf trace: Add upper bound checks for augmented BTF struct printing

[Aaron Tomlin]

When pretty-printing augmented struct payloads using BTF via
btf_struct_scnprintf(), augmented_arg->size is currently only validated
against values <= 0.

However, several edge cases can result in size mismatches or buffer
over-reads:
    1.  If arg->augmented.size is smaller than sizeof(*augmented_arg),
        dereferencing augmented_arg->size reads past the available
        buffer.

    2.  If augmented_arg->size exceeds arg->augmented.size -
        sizeof(*augmented_arg), calculating consumed =
        sizeof(*augmented_arg) + augmented_arg->size can overflow signed
        integer limits (e.g., with crafted INT_MAX values in an
        untrusted perf.data file) or cause arg->augmented.size to
        underflow. This advances arg->augmented.args out of bounds,
        corrupting the parsing state for subsequent arguments in
        multi-argument syscalls.

    3.  If the captured payload is truncated (e.g., short reads in BPF,
        or during cross-architecture analysis such as replaying a 32-bit
        perf.data on a 64-bit host where host BTF type->size exceeds the
        32-bit target payload), passing type->size to
        btf_dump__dump_type_data() causes libbpf to read past the end of
        the payload buffer.

Enforce an upper bound on augmented_arg->size against the remaining
buffer (arg->augmented.size - sizeof(*augmented_arg)) and verify that the
captured payload contains at least type->size bytes before passing it to
btf_dump__dump_type_data().

Fixes: cb32035214b9 ("perf trace: Pretty print struct data")
Reported-by: sashiko-bot <sashiko-bot@xxxxxxxxxx>
Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>
---
 tools/perf/builtin-trace.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index be19d70eba09..20fffc24507b 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1133,12 +1133,13 @@ static size_t btf_struct_scnprintf(const struct btf_type *type, struct btf *btf,
 	LIBBPF_OPTS(btf_dump_opts, dump_opts);
 	LIBBPF_OPTS(btf_dump_type_data_opts, dump_data_opts);
 
-	if (arg == NULL || arg->augmented.args == NULL || arg->augmented.size <= 0 ||
+	if (arg == NULL || arg->augmented.args == NULL || arg->augmented.size < (int)sizeof(*augmented_arg) ||
 	    arg->fmt == NULL || !arg->fmt->from_user)
 		return 0;
 
 	augmented_arg = arg->augmented.args;
-	if (augmented_arg->size <= 0)
+	if (augmented_arg->size <= 0 || augmented_arg->size > arg->augmented.size - (int)sizeof(*augmented_arg) ||
+	    (size_t)augmented_arg->size < type->size)
 		return 0;
 
 	dump_data_opts.compact	  = true;
-- 
2.55.0