Re: [PATCH v2 tracing 3/6] tracing: support IPv6 filter predicates
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2023-06-09 21:12:36
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BTW, the subjects for the tracing subsystem should always start with a capital letter. "tracing: Support IPv6 filter predicates" But that's not why I'm replying here. On Fri, 28 Apr 2023 16:34:46 +0100 Alan Maguire [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Support '==' and '!=' predicates for IPv6 addresses; for example cd /sys/kernel/debug/tracing/events/tcp/tcp_receive_reset echo "saddr_v6 == ::1" > filter or equivalently echo "saddr_v6 == 0:0:0:0:0:0:0:1" > filter Signed-off-by: Alan Maguire <redacted> --- kernel/trace/trace_events_filter.c | 73 ++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+)diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index d8e08d3c3594..e2521574f3c4 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c@@ -1665,6 +1665,79 @@ static int parse_pred(const char *str, void *data, if (pred->op == OP_NE) pred->not = 1; + } else if (field->size == 16 && + (str[i] == ':' || + (isalnum(str[i]) && tolower(str[i + 1]) != 'x'))) { + u8 j, gap_size, gap = 0, gap_count = 0, index = 0; + u16 tmp_v6addr[8] = {}; + u16 v6addr[8] = {}; + + /* For IPv6 addresses, only '==' or '!=' are supported. */ + if (pred->op != OP_EQ && pred->op != OP_NE) { + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i); + goto err_free; + } + /* Store the u16s in the address string consecutively in + * tmp_v6addr while tracking the presence of a "::" (if any) + * in the IPv6 address string; we will use its location + * to determine how many u16s it represents (the gap_size + * below). Only one "::" is allowed in an IPv6 address + * string. + */ + while (isalnum(str[i]) || str[i] == ':') { + switch (str[i]) { + case ':': + i++; + /* mark "::" index by setting gap */ + if (str[i] == ':') { + gap = index; + gap_count++; + i++; + } + if (gap_count > 1) { + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, + pos + s); + goto err_free; + } + break; + default: + if (sscanf(&str[i], "%hx", &tmp_v6addr[index]) != 1) { + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, + pos + s); + goto err_free; + } + index++; + while (isalnum(str[i])) + i++; + break; + } + }
There appears to be no limit to the above loop. I panic'd my machine with: # echo 'saddr_v6 == 0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef' > /sys/kernel/tracing/events/sock/inet_sk_error_report/filter -- Steve
+ /* The gap_size here represents the number of u16s the "::"
+ * represents; for ::1 the gap size is 7, for feed::face
+ * it is 6, etc.
+ */
+ gap_size = 8 - index;
+ index = 0;
+ for (j = 0; j < 8; ) {
+ if (gap_size > 0 && j == gap) {
+ j += gap_size;
+ } else {
+#ifdef __BIG_ENDIAN
+ v6addr[j++] = tmp_v6addr[index];
+#else
+ v6addr[j++] = ((tmp_v6addr[index] & 0xff) << 8) +
+ ((tmp_v6addr[index] & 0xff00) >> 8);
+#endif
+ index++;
+ }
+ }
+ pred_val = kzalloc(field->size, GFP_KERNEL);
+ memcpy(pred_val, v6addr, field->size);
+ pred->val = (u64)pred_val;
+ pred->fn_num = FILTER_PRED_FN_MEMCMP;
+ if (pred->op == OP_NE)
+ pred->not = 1;
+
} else if (str[i] == '0' && tolower(str[i + 1]) == 'x' &&
field->size > 8) {
/* For sizes > 8 bytes, we store hex bytes for comparison;