Fix: statedump: missing locking, use lttng_iterate_fd

- Take a spinlock around use of dentry->d_name.name.
- Use lttng_iterate_fd wrapper (and thus iterate_fd() from Linux kernels
  from v3.7 and onward).

Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/Makefile b/Makefile
index 4cc8b6bf429a47288adef4c69707c337cc4d97a0..2da72989e4c75a27ab4270e891a5b2c6950cadff 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -23,7 +23,8 @@ lttng-tracer-objs :=  lttng-events.o lttng-abi.o \
                        lttng-context-hostname.o wrapper/random.o
 
 obj-m += lttng-statedump.o
-lttng-statedump-objs := lttng-statedump-impl.o wrapper/irqdesc.o
+lttng-statedump-objs := lttng-statedump-impl.o wrapper/irqdesc.o \
+                       wrapper/fdtable.o
 
 ifneq ($(CONFIG_HAVE_SYSCALL_TRACEPOINTS),)
 lttng-tracer-objs += lttng-syscalls.o probes/lttng-probe-user.o

diff --git a/lttng-statedump-impl.c b/lttng-statedump-impl.c
index bbe0a15652475b316f663a811bc08dff32c6a88d..04acf6eff3409beb78944fad9476d44c74098cec 100644 (file)
--- a/lttng-statedump-impl.c
+++ b/lttng-statedump-impl.c
@@ -49,6 +49,7 @@
 #include "lttng-events.h"
 #include "wrapper/irqdesc.h"
 #include "wrapper/spinlock.h"
+#include "wrapper/fdtable.h"
 
 #ifdef CONFIG_GENERIC_HARDIRQS
 #include <linux/irq.h>
@@ -60,6 +61,12 @@
 #define TRACE_INCLUDE_FILE lttng-statedump
 #include "instrumentation/events/lttng-module/lttng-statedump.h"
 
+struct lttng_fd_ctx {
+       char *page;
+       struct lttng_session *session;
+       struct task_struct *p;
+};
+
 /*
  * Protected by the trace lock.
  */
@@ -141,34 +148,35 @@ int lttng_enumerate_network_ip_interface(struct lttng_session *session)
 }
 #endif /* CONFIG_INET */
 
+static
+int lttng_dump_one_fd(const void *p, struct file *file, unsigned int fd)
+{
+       const struct lttng_fd_ctx *ctx = p;
+       const char *s = d_path(&file->f_path, ctx->page, PAGE_SIZE);
+
+       if (IS_ERR(s)) {
+               struct dentry *dentry = file->f_path.dentry;
+
+               /* Make sure we give at least some info */
+               spin_lock(&dentry->d_lock);
+               trace_lttng_statedump_file_descriptor(ctx->session, ctx->p, fd,
+                       dentry->d_name.name);
+               spin_unlock(&dentry->d_lock);
+               goto end;
+       }
+       trace_lttng_statedump_file_descriptor(ctx->session, ctx->p, fd, s);
+end:
+       return 0;
+}
 
 static
 void lttng_enumerate_task_fd(struct lttng_session *session,
                struct task_struct *p, char *tmp)
 {
-       struct fdtable *fdt;
-       struct file *filp;
-       unsigned int i;
-       const unsigned char *path;
+       struct lttng_fd_ctx ctx = { .page = tmp, .session = session, .p = p };
 
        task_lock(p);
-       if (!p->files)
-               goto unlock_task;
-       spin_lock(&p->files->file_lock);
-       fdt = files_fdtable(p->files);
-       for (i = 0; i < fdt->max_fds; i++) {
-               filp = fcheck_files(p->files, i);
-               if (!filp)
-                       continue;
-               path = d_path(&filp->f_path, tmp, PAGE_SIZE);
-               /* Make sure we give at least some info */
-               trace_lttng_statedump_file_descriptor(session, p, i,
-                       IS_ERR(path) ?
-                               filp->f_dentry->d_name.name :
-                               path);
-       }
-       spin_unlock(&p->files->file_lock);
-unlock_task:
+       lttng_iterate_fd(p->files, 0, lttng_dump_one_fd, &ctx);
        task_unlock(p);
 }