[PATCH v2 perf-tools-next 3/6] perf trace: Validate payload bounds in augmented buffer beautifier

[Aaron Tomlin <atomlin@atomlin.com>]

When pretty-printing non-string augmented buffers via
syscall_arg__scnprintf_buf(), augmented_arg->size is not validated
against the remaining buffer size (arg->augmented.size).

If a malformed or truncated perf.data record provides an invalid or
excessively large augmented_arg->size:
    1.  If arg->augmented.size is smaller than sizeof(*augmented_arg),
        dereferencing augmented_arg->size reads past the available
        buffer.

    2.  The loop reads up to augmented_arg->size bytes from
        augmented_arg->value without verifying that they exist within
        the buffer, leading to buffer over-reads.

    3.  Calculating consumed = sizeof(*augmented_arg) +
        augmented_arg->size can overflow signed integer bounds or cause
        arg->augmented.size to underflow, advancing arg->augmented.args
        out of bounds and corrupting the parsing state for subsequent
        arguments in multi-argument syscalls.

Validate that arg->augmented.size is large enough to hold
sizeof(*augmented_arg) and that augmented_arg->size is within the bounds
of the remaining buffer before iterating or calculating consumed bytes.
If validation fails, fall back to printing the raw pointer value.

Fixes: b257fac12f38 ("perf trace: Pretty print buffer data")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/builtin-trace.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 91461ab927b6..4277de761a54 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1945,13 +1945,17 @@ static size_t syscall_arg__scnprintf_filename(char *bf, size_t size,
 static size_t syscall_arg__scnprintf_buf(char *bf, size_t size, struct syscall_arg *arg)
 {
 	struct augmented_arg *augmented_arg = arg->augmented.args;
-	unsigned char *orig = (unsigned char *)augmented_arg->value;
+	unsigned char *orig;
 	size_t printed = 0;
 	int consumed;
 
-	if (augmented_arg == NULL)
-		return 0;
+	if (augmented_arg == NULL || arg->augmented.size < (int)sizeof(*augmented_arg))
+		return scnprintf(bf, size, "%#lx", arg->val);
+
+	if (augmented_arg->size <= 0 || augmented_arg->size > arg->augmented.size - (int)sizeof(*augmented_arg))
+		return scnprintf(bf, size, "%#lx", arg->val);
 
+	orig = (unsigned char *)augmented_arg->value;
 	for (int j = 0; j < augmented_arg->size; ++j) {
 		bool control_char = orig[j] <= MAX_CONTROL_CHAR || orig[j] >= MAX_ASCII;
 		/* print control characters (0~31 and 127), and non-ascii characters in \(digits) */
-- 
2.55.0