From 4cc896ea5f06f8b1ebcde6d876d9c5b59ef9a016 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Thu, 7 Apr 2016 17:26:56 +0200 Subject: [PATCH] avformat/format: Fix registering a format more than once and related races Signed-off-by: Michael Niedermayer --- libavformat/format.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/libavformat/format.c b/libavformat/format.c index 7fa06a68be3..38ca2a3465a 100644 --- a/libavformat/format.c +++ b/libavformat/format.c @@ -62,20 +62,24 @@ void av_register_input_format(AVInputFormat *format) { AVInputFormat **p = last_iformat; - format->next = NULL; - while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format)) + // Note, format could be added after the first 2 checks but that implies that *p is no longer NULL + while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format)) p = &(*p)->next; - last_iformat = &format->next; + + if (!format->next) + last_iformat = &format->next; } void av_register_output_format(AVOutputFormat *format) { AVOutputFormat **p = last_oformat; - format->next = NULL; - while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format)) + // Note, format could be added after the first 2 checks but that implies that *p is no longer NULL + while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format)) p = &(*p)->next; - last_oformat = &format->next; + + if (!format->next) + last_oformat = &format->next; } int av_match_ext(const char *filename, const char *extensions) -- 2.39.2