[PATCH v5 15/17] perf namespaces: Add reference count checking

Ian Rogers
2023-03-20T21:26:17Z

Add reference count checking controlled by REFCNT_CHECKING ifdef. The
reference count checking interposes an allocated pointer between the
reference counted struct on a get and frees the pointer on a put.
Accesses after a put cause faults and use after free, missed puts are
caughts as leaks and double puts are double frees.

This checking helped resolve a memory leak and use after free:
https://lore.kernel.org/linux-perf-users/CAP-5=fWZH20L4kv-BwVtGLwR=Em3AOOT+Q4QGivvQuYn5AsPRg@mail.gmail.com/

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/builtin-inject.c | 2 +-
tools/perf/util/annotate.c | 2 +-
tools/perf/util/dso.c | 2 +-
tools/perf/util/dsos.c | 2 +-
tools/perf/util/namespaces.c | 132 ++++++++++++++++++++---------------
tools/perf/util/namespaces.h | 3 +-
tools/perf/util/symbol.c | 2 +-
7 files changed, 83 insertions(+), 62 deletions(-)

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index fd2b38458a5d..fe6ddcf7fb1e 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -632,7 +632,7 @@ static int dso__read_build_id(struct dso *dso)
else if (dso->nsinfo) {
char *new_name;

- new_name = filename_with_chroot(dso->nsinfo->pid,
+ new_name = filename_with_chroot(RC_CHK_ACCESS(dso->nsinfo)->pid,
dso->long_name);
if (new_name && filename__read_build_id(new_name, &dso->bid) > 0)
dso->has_build_id = true;
diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index e8570b7cc36f..199f6cd5ad1e 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1701,7 +1701,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil

mutex_lock(&dso->lock);
if (access(filename, R_OK) && errno == ENOENT && dso->nsinfo) {
- char *new_name = filename_with_chroot(dso->nsinfo->pid,
+ char *new_name = filename_with_chroot(RC_CHK_ACCESS(dso->nsinfo)->pid,
filename);
if (new_name) {
strlcpy(filename, new_name, filename_size);
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index e36b418df2c6..6c4129598f5d 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -515,7 +515,7 @@ static int __open_dso(struct dso *dso, struct machine *machine)
if (errno != ENOENT || dso->nsinfo == NULL)
goto out;

- new_name = filename_with_chroot(dso->nsinfo->pid, name);
+ new_name = filename_with_chroot(RC_CHK_ACCESS(dso->nsinfo)->pid, name);
if (!new_name)
goto out;

diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
index 2bd23e4cf19e..53b989072ec5 100644
--- a/tools/perf/util/dsos.c
+++ b/tools/perf/util/dsos.c
@@ -91,7 +91,7 @@ bool __dsos__read_build_ids(struct list_head *head, bool with_hits)
have_build_id = true;
pos->has_build_id = true;
} else if (errno == ENOENT && pos->nsinfo) {
- char *new_name = filename_with_chroot(pos->nsinfo->pid,
+ char *new_name = filename_with_chroot(RC_CHK_ACCESS(pos->nsinfo)->pid,
pos->long_name);

if (new_name && filename__read_build_id(new_name,
diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index dd536220cdb9..8a3b7bd27b19 100644
--- a/tools/perf/util/namespaces.c
+++ b/tools/perf/util/namespaces.c
@@ -60,7 +60,7 @@ void namespaces__free(struct namespaces *namespaces)
free(namespaces);
}

-static int nsinfo__get_nspid(struct nsinfo *nsi, const char *path)
+static int nsinfo__get_nspid(pid_t *tgid, pid_t *nstgid, bool *in_pidns, const char *path)
{
FILE *f = NULL;
char *statln = NULL;
@@ -74,19 +74,18 @@ static int nsinfo__get_nspid(struct nsinfo *nsi, const char *path)
while (getline(&statln, &linesz, f) != -1) {
/* Use tgid if CONFIG_PID_NS is not defined. */
if (strstr(statln, "Tgid:") != NULL) {
- nsi->tgid = (pid_t)strtol(strrchr(statln, '\t'),
- NULL, 10);
- nsi->nstgid = nsinfo__tgid(nsi);
+ *tgid = (pid_t)strtol(strrchr(statln, '\t'), NULL, 10);
+ *nstgid = *tgid;
}

if (strstr(statln, "NStgid:") != NULL) {
nspid = strrchr(statln, '\t');
- nsi->nstgid = (pid_t)strtol(nspid, NULL, 10);
+ *nstgid = (pid_t)strtol(nspid, NULL, 10);
/*
* If innermost tgid is not the first, process is in a different
* PID namespace.
*/
- nsi->in_pidns = (statln + sizeof("NStgid:") - 1) != nspid;
+ *in_pidns = (statln + sizeof("NStgid:") - 1) != nspid;
break;
}
}
@@ -121,8 +120,8 @@ int nsinfo__init(struct nsinfo *nsi)
* want to switch as part of looking up dso/map data.
*/
if (old_stat.st_ino != new_stat.st_ino) {
- nsi->need_setns = true;
- nsi->mntns_path = newns;
+ RC_CHK_ACCESS(nsi)->need_setns = true;
+ RC_CHK_ACCESS(nsi)->mntns_path = newns;
newns = NULL;
}

@@ -132,13 +131,26 @@ int nsinfo__init(struct nsinfo *nsi)
if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsinfo__pid(nsi)) >= PATH_MAX)
goto out;

- rv = nsinfo__get_nspid(nsi, spath);
+ rv = nsinfo__get_nspid(&RC_CHK_ACCESS(nsi)->tgid, &RC_CHK_ACCESS(nsi)->nstgid,
+ &RC_CHK_ACCESS(nsi)->in_pidns, spath);

out:
free(newns);
return rv;
}

+static struct nsinfo *nsinfo__alloc(void)
+{
+ struct nsinfo *res;
+ RC_STRUCT(nsinfo) *nsi;
+
+ nsi = calloc(1, sizeof(*nsi));
+ if (ADD_RC_CHK(res, nsi))
+ refcount_set(&nsi->refcnt, 1);
+
+ return res;
+}
+
struct nsinfo *nsinfo__new(pid_t pid)
{
struct nsinfo *nsi;
@@ -146,22 +158,21 @@ struct nsinfo *nsinfo__new(pid_t pid)
if (pid == 0)
return NULL;

- nsi = calloc(1, sizeof(*nsi));
- if (nsi != NULL) {
- nsi->pid = pid;
- nsi->tgid = pid;
- nsi->nstgid = pid;
- nsi->need_setns = false;
- nsi->in_pidns = false;
- /* Init may fail if the process exits while we're trying to look
- * at its proc information. In that case, save the pid but
- * don't try to enter the namespace.
- */
- if (nsinfo__init(nsi) == -1)
- nsi->need_setns = false;
+ nsi = nsinfo__alloc();
+ if (!nsi)
+ return NULL;

- refcount_set(&nsi->refcnt, 1);
- }
+ RC_CHK_ACCESS(nsi)->pid = pid;
+ RC_CHK_ACCESS(nsi)->tgid = pid;
+ RC_CHK_ACCESS(nsi)->nstgid = pid;
+ RC_CHK_ACCESS(nsi)->need_setns = false;
+ RC_CHK_ACCESS(nsi)->in_pidns = false;
+ /* Init may fail if the process exits while we're trying to look at its
+ * proc information. In that case, save the pid but don't try to enter
+ * the namespace.
+ */
+ if (nsinfo__init(nsi) == -1)
+ RC_CHK_ACCESS(nsi)->need_setns = false;

return nsi;
}
@@ -173,21 +184,21 @@ struct nsinfo *nsinfo__copy(const struct nsinfo *nsi)
if (nsi == NULL)
return NULL;

- nnsi = calloc(1, sizeof(*nnsi));
- if (nnsi != NULL) {
- nnsi->pid = nsinfo__pid(nsi);
- nnsi->tgid = nsinfo__tgid(nsi);
- nnsi->nstgid = nsinfo__nstgid(nsi);
- nnsi->need_setns = nsinfo__need_setns(nsi);
- nnsi->in_pidns = nsinfo__in_pidns(nsi);
- if (nsi->mntns_path) {
- nnsi->mntns_path = strdup(nsi->mntns_path);
- if (!nnsi->mntns_path) {
- free(nnsi);
- return NULL;
- }
+ nnsi = nsinfo__alloc();
+ if (!nnsi)
+ return NULL;
+
+ RC_CHK_ACCESS(nnsi)->pid = nsinfo__pid(nsi);
+ RC_CHK_ACCESS(nnsi)->tgid = nsinfo__tgid(nsi);
+ RC_CHK_ACCESS(nnsi)->nstgid = nsinfo__nstgid(nsi);
+ RC_CHK_ACCESS(nnsi)->need_setns = nsinfo__need_setns(nsi);
+ RC_CHK_ACCESS(nnsi)->in_pidns = nsinfo__in_pidns(nsi);
+ if (RC_CHK_ACCESS(nsi)->mntns_path) {
+ RC_CHK_ACCESS(nnsi)->mntns_path = strdup(RC_CHK_ACCESS(nsi)->mntns_path);
+ if (!RC_CHK_ACCESS(nnsi)->mntns_path) {
+ nsinfo__put(nnsi);
+ return NULL;
}
- refcount_set(&nnsi->refcnt, 1);
}

return nnsi;
@@ -195,51 +206,60 @@ struct nsinfo *nsinfo__copy(const struct nsinfo *nsi)

static void nsinfo__delete(struct nsinfo *nsi)
{
- zfree(&nsi->mntns_path);
- free(nsi);
+ if (nsi) {
+ WARN_ONCE(refcount_read(&RC_CHK_ACCESS(nsi)->refcnt) != 0,
+ "nsinfo refcnt unbalanced\n");
+ zfree(&RC_CHK_ACCESS(nsi)->mntns_path);
+ RC_CHK_FREE(nsi);
+ }
}

struct nsinfo *nsinfo__get(struct nsinfo *nsi)
{
- if (nsi)
- refcount_inc(&nsi->refcnt);
- return nsi;
+ struct nsinfo *result;
+
+ if (RC_CHK_GET(result, nsi))
+ refcount_inc(&RC_CHK_ACCESS(nsi)->refcnt);
+
+ return result;
}

void nsinfo__put(struct nsinfo *nsi)
{
- if (nsi && refcount_dec_and_test(&nsi->refcnt))
+ if (nsi && refcount_dec_and_test(&RC_CHK_ACCESS(nsi)->refcnt))
nsinfo__delete(nsi);
+ else
+ RC_CHK_PUT(nsi);
}

bool nsinfo__need_setns(const struct nsinfo *nsi)
{
- return nsi->need_setns;
+ return RC_CHK_ACCESS(nsi)->need_setns;
}

void nsinfo__clear_need_setns(struct nsinfo *nsi)
{
- nsi->need_setns = false;
+ RC_CHK_ACCESS(nsi)->need_setns = false;
}

pid_t nsinfo__tgid(const struct nsinfo *nsi)
{
- return nsi->tgid;
+ return RC_CHK_ACCESS(nsi)->tgid;
}

pid_t nsinfo__nstgid(const struct nsinfo *nsi)
{
- return nsi->nstgid;
+ return RC_CHK_ACCESS(nsi)->nstgid;
}

pid_t nsinfo__pid(const struct nsinfo *nsi)
{
- return nsi->pid;
+ return RC_CHK_ACCESS(nsi)->pid;
}

pid_t nsinfo__in_pidns(const struct nsinfo *nsi)
{
- return nsi->in_pidns;
+ return RC_CHK_ACCESS(nsi)->in_pidns;
}

void nsinfo__mountns_enter(struct nsinfo *nsi,
@@ -256,7 +276,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
nc->oldns = -1;
nc->newns = -1;

- if (!nsi || !nsi->need_setns)
+ if (!nsi || !RC_CHK_ACCESS(nsi)->need_setns)
return;

if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
@@ -270,7 +290,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
if (oldns < 0)
goto errout;

- newns = open(nsi->mntns_path, O_RDONLY);
+ newns = open(RC_CHK_ACCESS(nsi)->mntns_path, O_RDONLY);
if (newns < 0)
goto errout;

@@ -339,9 +359,9 @@ int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi)

bool nsinfo__is_in_root_namespace(void)
{
- struct nsinfo nsi;
+ pid_t tgid = 0, nstgid = 0;
+ bool in_pidns = false;

- memset(&nsi, 0x0, sizeof(nsi));
- nsinfo__get_nspid(&nsi, "/proc/self/status");
- return !nsi.in_pidns;
+ nsinfo__get_nspid(&tgid, &nstgid, &in_pidns, "/proc/self/status");
+ return !in_pidns;
}
diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h
index 567829262c42..8c0731c6cbb7 100644
--- a/tools/perf/util/namespaces.h
+++ b/tools/perf/util/namespaces.h
@@ -13,6 +13,7 @@
#include <linux/perf_event.h>
#include <linux/refcount.h>
#include <linux/types.h>
+#include <internal/rc_check.h>

#ifndef HAVE_SETNS_SUPPORT
int setns(int fd, int nstype);
@@ -29,7 +30,7 @@ struct namespaces {
struct namespaces *namespaces__new(struct perf_record_namespaces *event);
void namespaces__free(struct namespaces *namespaces);

-struct nsinfo {
+DECLARE_RC_STRUCT(nsinfo) {
pid_t pid;
pid_t tgid;
pid_t nstgid;
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 7904bfff7d0e..f5432c7add09 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1962,7 +1962,7 @@ int dso__load(struct dso *dso, struct map *map)

is_reg = is_regular_file(name);
if (!is_reg && errno == ENOENT && dso->nsinfo) {
- char *new_name = filename_with_chroot(dso->nsinfo->pid,
+ char *new_name = filename_with_chroot(RC_CHK_ACCESS(dso->nsinfo)->pid,
name);
if (new_name) {
is_reg = is_regular_file(new_name);
--
2.40.0.rc1.284.g88254d51c5-goog