the resourcenot release in time when file be truncated

[Dane Zhang]

1,a client request a file;
2,nginx response the request use sendfile,;
3,the file be truncated (rsync etc)
4,nginx have not detect this condition in time;
5,nginx release the resource (local fd and socket) after time out;

patch:
--- ngx_linux_sendfile_chain.c 2014-02-14 11:18:43.772856547 +0800
+++ ngx_linux_sendfile_chain.c 2014-02-14 14:28:55.644845942 +0800
@@ -286,6 +286,22 @@

sent = rc > 0 ? rc : 0;

+ if (rc == 0)
+ {
+ ngx_file_info_t new_info;
+ if (ngx_file_info(file->file->name.data, &new_info) == 0)
+ {
+ if (new_info.st_size < file->file_last)
+ {
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "sendfile error: %d, %s, %O < %O",
+ rc, file->file->name.data, new_info.st_size, file->file_last);
+ wev->error = 1;
+ return NGX_CHAIN_ERROR;
+ }
+ }
+ }
+

[Leslie Zhai]

because the FILE has been CHANGED, if the total size (in bytes) new_info.st_size is smaller than file_last (defined in struct ngx_buf_s), perhaps the file_pos was also changed!

[Maxim Dounin]

Truncation detection for sendfile() on Linux and Solaris was added in nginx 1.9.13, see 4df3d9fcdee8 and 646985c55393. File truncation is properly detected now on these platforms as well and results in "sendfile() reported that ... was truncated at ..." alerts, much like on FreeBSD and OS X.