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Date: Wed, 5 Oct 2016 08:45:24 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Krister Johansen <kjlx@...pleofstupid.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Frédéric Weisbecker <fweisbec@...il.com>,
linux-kernel@...r.kernel.org
Subject: callchain map refcounting fixes was Re: [PATCH perf/core] perf
script: fix a use after free crash.
Em Sat, Oct 01, 2016 at 08:13:36PM -0700, Krister Johansen escreveu:
> If dso__load_kcore frees all of the existing maps, but one has already
> been attached to a callchain cursor node, then we can get a SIGSEGV in
> any function that happens to try to use this cursor with the invalid
> map. Use the existing map refcount mechanism to forestall cleanup of a
> map until the cursor iterates past the node.
Seems ok, thanks for working on this! Can you provide a test case that
causes the SEGV so that I can, in addition to reviewing your changes and
auditing the code to check if all cases ara plugged, to reproduce the
problem?
Frédéric, Namhyung, Ack?
Masami, is this a case that your refcount validator can catch?
- Arnaldo
> Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
> ---
> tools/perf/util/callchain.c | 12 ++++++++++--
> tools/perf/util/callchain.h | 20 ++++++++++++++++++++
> tools/perf/util/hist.c | 4 ++++
> 3 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> index 07fd30b..15c89b2 100644
> --- a/tools/perf/util/callchain.c
> +++ b/tools/perf/util/callchain.c
> @@ -439,7 +439,7 @@ fill_node(struct callchain_node *node, struct callchain_cursor *cursor)
> }
> call->ip = cursor_node->ip;
> call->ms.sym = cursor_node->sym;
> - call->ms.map = cursor_node->map;
> + call->ms.map = map__get(cursor_node->map);
> list_add_tail(&call->list, &node->val);
>
> callchain_cursor_advance(cursor);
> @@ -464,6 +464,7 @@ add_child(struct callchain_node *parent,
>
> list_for_each_entry_safe(call, tmp, &new->val, list) {
> list_del(&call->list);
> + map__zput(call->ms.map);
> free(call);
> }
> free(new);
> @@ -732,6 +733,7 @@ merge_chain_branch(struct callchain_cursor *cursor,
> callchain_cursor_append(cursor, list->ip,
> list->ms.map, list->ms.sym);
> list_del(&list->list);
> + map__zput(list->ms.map);
> free(list);
> }
>
> @@ -780,7 +782,8 @@ int callchain_cursor_append(struct callchain_cursor *cursor,
> }
>
> node->ip = ip;
> - node->map = map;
> + map__zput(node->map);
> + node->map = map__get(map);
> node->sym = sym;
>
> cursor->nr++;
> @@ -830,6 +833,8 @@ int fill_callchain_info(struct addr_location *al, struct callchain_cursor_node *
> goto out;
> }
>
> + map__get(al->map);
> +
> if (al->map->groups == &al->machine->kmaps) {
> if (machine__is_host(al->machine)) {
> al->cpumode = PERF_RECORD_MISC_KERNEL;
> @@ -947,11 +952,13 @@ static void free_callchain_node(struct callchain_node *node)
>
> list_for_each_entry_safe(list, tmp, &node->parent_val, list) {
> list_del(&list->list);
> + map__zput(list->ms.map);
> free(list);
> }
>
> list_for_each_entry_safe(list, tmp, &node->val, list) {
> list_del(&list->list);
> + map__zput(list->ms.map);
> free(list);
> }
>
> @@ -1035,6 +1042,7 @@ int callchain_node__make_parent_list(struct callchain_node *node)
> out:
> list_for_each_entry_safe(chain, new, &head, list) {
> list_del(&chain->list);
> + map__zput(chain->ms.map);
> free(chain);
> }
> return -ENOMEM;
> diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
> index 13e7554..0d944ef 100644
> --- a/tools/perf/util/callchain.h
> +++ b/tools/perf/util/callchain.h
> @@ -5,6 +5,7 @@
> #include <linux/list.h>
> #include <linux/rbtree.h>
> #include "event.h"
> +#include "map.h"
> #include "symbol.h"
>
> #define HELP_PAD "\t\t\t\t"
> @@ -178,8 +179,13 @@ int callchain_merge(struct callchain_cursor *cursor,
> */
> static inline void callchain_cursor_reset(struct callchain_cursor *cursor)
> {
> + struct callchain_cursor_node *node;
> +
> cursor->nr = 0;
> cursor->last = &cursor->first;
> +
> + for (node = cursor->first; node != NULL; node = node->next)
> + map__zput(node->map);
> }
>
> int callchain_cursor_append(struct callchain_cursor *cursor, u64 ip,
> @@ -238,12 +244,26 @@ int perf_callchain_config(const char *var, const char *value);
> static inline void callchain_cursor_snapshot(struct callchain_cursor *dest,
> struct callchain_cursor *src)
> {
> + struct callchain_cursor_node *node;
> +
> *dest = *src;
>
> dest->first = src->curr;
> dest->nr -= src->pos;
> +
> + for (node = dest->first; node != NULL; node = node->next)
> + map__get(node->map);
> }
>
> +static inline void callchain_cursor_snapshot_rele(struct callchain_cursor *curs)
> +{
> + struct callchain_cursor_node *node;
> +
> + for (node = curs->first; node != NULL; node = node->next)
> + map__put(node->map);
> +}
> +
> +
> #ifdef HAVE_SKIP_CALLCHAIN_IDX
> int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain);
> #else
> diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> index b02992e..f8335e8 100644
> --- a/tools/perf/util/hist.c
> +++ b/tools/perf/util/hist.c
> @@ -1,6 +1,7 @@
> #include "util.h"
> #include "build-id.h"
> #include "hist.h"
> +#include "map.h"
> #include "session.h"
> #include "sort.h"
> #include "evlist.h"
> @@ -970,6 +971,8 @@ iter_add_next_cumulative_entry(struct hist_entry_iter *iter,
>
> if (symbol_conf.use_callchain)
> callchain_append(he->callchain, &cursor, sample->period);
> + /* Cleanup temporary cursor. */
> + callchain_cursor_snapshot_rele(&cursor);
> return 0;
> }
>
> @@ -979,6 +982,7 @@ iter_finish_cumulative_entry(struct hist_entry_iter *iter,
> {
> zfree(&iter->priv);
> iter->he = NULL;
> + map__zput(al->map);
>
> return 0;
> }
> --
> 2.7.4
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