From ea635c64e007061f6468ece5cc9cc62d41d4ecf2 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 26 May 2010 17:40:29 -0400 Subject: [PATCH] Fix racy use of anon_inode_getfd() in perf_event.c once anon_inode_getfd() is called, you can't expect *anything* about struct file that descriptor points to - another thread might be doing whatever it likes with descriptor table at that point. Cc: stable Signed-off-by: Al Viro --- kernel/perf_event.c | 40 ++++++++++++++++++++++------------------ 1 file changed, 22 insertions(+), 18 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index e099650cd249..bd7ce8ca5bb9 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -4999,8 +4999,8 @@ SYSCALL_DEFINE5(perf_event_open, struct perf_event_context *ctx; struct file *event_file = NULL; struct file *group_file = NULL; + int event_fd; int fput_needed = 0; - int fput_needed2 = 0; int err; /* for future expandability... */ @@ -5021,12 +5021,18 @@ SYSCALL_DEFINE5(perf_event_open, return -EINVAL; } + event_fd = get_unused_fd_flags(O_RDWR); + if (event_fd < 0) + return event_fd; + /* * Get the target context (task or percpu): */ ctx = find_get_context(pid, cpu); - if (IS_ERR(ctx)) - return PTR_ERR(ctx); + if (IS_ERR(ctx)) { + err = PTR_ERR(ctx); + goto err_fd; + } /* * Look up the group leader (we will attach this event to it): @@ -5066,13 +5072,11 @@ SYSCALL_DEFINE5(perf_event_open, if (IS_ERR(event)) goto err_put_context; - err = anon_inode_getfd("[perf_event]", &perf_fops, event, O_RDWR); - if (err < 0) - goto err_free_put_context; - - event_file = fget_light(err, &fput_needed2); - if (!event_file) + event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, O_RDWR); + if (IS_ERR(event_file)) { + err = PTR_ERR(event_file); goto err_free_put_context; + } if (flags & PERF_FLAG_FD_OUTPUT) { err = perf_event_set_output(event, group_fd); @@ -5093,19 +5097,19 @@ SYSCALL_DEFINE5(perf_event_open, list_add_tail(&event->owner_entry, ¤t->perf_event_list); mutex_unlock(¤t->perf_event_mutex); -err_fput_free_put_context: - fput_light(event_file, fput_needed2); + fput_light(group_file, fput_needed); + fd_install(event_fd, event_file); + return event_fd; +err_fput_free_put_context: + fput(event_file); err_free_put_context: - if (err < 0) - free_event(event); - + free_event(event); err_put_context: - if (err < 0) - put_ctx(ctx); - fput_light(group_file, fput_needed); - + put_ctx(ctx); +err_fd: + put_unused_fd(event_fd); return err; } -- 2.39.5