Messages in this thread Patch in this message | | | Date | Tue, 4 Feb 2014 18:28:52 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH] exec: Fix use after free of tracepoint trace_sched_process_exec |
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On Tue, 4 Feb 2014 12:18:53 -0800 Linus Torvalds <torvalds@linux-foundation.org> wrote: > > That's too ugly to live.
New patch. Not as ugly. Well, I think this one lacks ugly enough to be worth living for.
It's dependent on another patch that adds a helper function for tracepoints, that allows users to implicitly use static_key of a tracepoint to see if it is enabled or not. Basically, it's:
#define tracepoint_enabled(name) \ static_key_false(&__tracepoint_##name.key)
This uses the same key that the tracepoint has when it is enabled. It may be enabled before or after the tracepoint is, but in cases like these, it doesn't really matter.
At least this patch keeps the ugliness with the code. I could even encapsulate that in a static inline function to remove the ugliness out of exec_binprm().
Note, this still requires some comments added to the code.
Butt-ugly-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/fs/exec.c b/fs/exec.c index e1529b4..f7902aef 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1421,7 +1421,22 @@ static int exec_binprm(struct linux_binprm *bprm) ret = search_binary_handler(bprm); if (ret >= 0) { audit_bprm(bprm); - trace_sched_process_exec(current, old_pid, bprm); + if (tracepoint_enabled(sched_process_exec)) { + char *tmp = (char*)__get_free_page(GFP_TEMPORARY); + char *pathname; + + if (tmp) + pathname = dentry_path_raw(bprm->file->f_dentry, + tmp, PAGE_SIZE); + else + pathname = ERR_PTR(-ENOMEM); + if (IS_ERR(pathname)) + trace_sched_process_exec(current, old_pid, + "//error-no-mem"); + else + trace_sched_process_exec(current, old_pid, pathname); + free_page((unsigned long)tmp); + } ptrace_event(PTRACE_EVENT_EXEC, old_vpid); proc_exec_connector(current); } diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index 67e1bbf..520ba9a 100644 --- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h @@ -282,18 +282,18 @@ TRACE_EVENT(sched_process_fork, TRACE_EVENT(sched_process_exec, TP_PROTO(struct task_struct *p, pid_t old_pid, - struct linux_binprm *bprm), + const char *pathname), - TP_ARGS(p, old_pid, bprm), + TP_ARGS(p, old_pid, pathname), TP_STRUCT__entry( - __string( filename, bprm->filename ) + __string( filename, pathname ) __field( pid_t, pid ) __field( pid_t, old_pid ) ), TP_fast_assign( - __assign_str(filename, bprm->filename); + __assign_str(filename, pathname); __entry->pid = p->pid; __entry->old_pid = old_pid; ),
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