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authorLudovic Courtès <ludo@gnu.org>2017-11-19 23:02:29 +0100
committerLudovic Courtès <ludo@gnu.org>2017-11-19 23:09:01 +0100
commit85f4f7b79040d982c6a655c898b4cd00d868fa9c (patch)
tree4cc7fa226e57fed5f4269f0eb8e3d61af7d2c7a0 /guix/zlib.scm
parent52d174d6d116d75c71ddf0aa448b05f58637e9df (diff)
zlib: Fix race condition when closing gzip ports.
Fixes <https://bugs.gnu.org/29335>. * guix/zlib.scm (close-procedure): Remove. (make-gzip-input-port): Do (dup (fileno port)) to get a file descriptor for 'gzdopen'. Close PORT before returning. Use 'gzclose' as the 'close' procedure of the returned port. (make-gzip-output-port): Likewise.
Diffstat (limited to 'guix/zlib.scm')
-rw-r--r--guix/zlib.scm46
1 files changed, 16 insertions, 30 deletions
diff --git a/guix/zlib.scm b/guix/zlib.scm
index 955589ab48..3bd0ad86c9 100644
--- a/guix/zlib.scm
+++ b/guix/zlib.scm
@@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
@@ -149,31 +149,6 @@ the number of uncompressed bytes written, a strictly positive integer."
;; Z_DEFAULT_COMPRESSION.
-1)
-(define (close-procedure gzfile port)
- "Return a procedure that closes GZFILE, ensuring its underlying PORT is
-closed even if closing GZFILE triggers an exception."
- (let-syntax ((ignore-EBADF
- (syntax-rules ()
- ((_ exp)
- (catch 'system-error
- (lambda ()
- exp)
- (lambda args
- (unless (= EBADF (system-error-errno args))
- (apply throw args))))))))
-
- (lambda ()
- (catch 'zlib-error
- (lambda ()
- ;; 'gzclose' closes the underlying file descriptor. 'close-port'
- ;; calls close(2) and gets EBADF, which we swallow.
- (gzclose gzfile)
- (ignore-EBADF (close-port port)))
- (lambda args
- ;; Make sure PORT is closed despite the zlib error.
- (ignore-EBADF (close-port port))
- (apply throw args))))))
-
(define* (make-gzip-input-port port #:key (buffer-size %default-buffer-size))
"Return an input port that decompresses data read from PORT, a file port.
PORT is automatically closed when the resulting port is closed. BUFFER-SIZE
@@ -183,7 +158,14 @@ buffered input, which would be lost (and is lost anyway)."
(define gzfile
(match (drain-input port)
("" ;PORT's buffer is empty
- (gzdopen (fileno port) "r"))
+ ;; 'gzclose' will eventually close the file descriptor beneath PORT.
+ ;; 'close-port' on PORT would get EBADF if 'gzclose' already closed it,
+ ;; so that's no good; revealed ports are no good either because they
+ ;; leak (see <https://bugs.gnu.org/28784>); calling 'close-port' after
+ ;; 'gzclose' doesn't work either because it leads to a race condition
+ ;; (see <https://bugs.gnu.org/29335>). So we dup and close PORT right
+ ;; away.
+ (gzdopen (dup (fileno port)) "r"))
(_
;; This is unrecoverable but it's better than having the buffered input
;; be lost, leading to unclear end-of-file or corrupt-data errors down
@@ -197,8 +179,10 @@ buffered input, which would be lost (and is lost anyway)."
(unless (= buffer-size %default-buffer-size)
(gzbuffer! gzfile buffer-size))
+ (close-port port) ;we no longer need it
(make-custom-binary-input-port "gzip-input" read! #f #f
- (close-procedure gzfile port)))
+ (lambda ()
+ (gzclose gzfile))))
(define* (make-gzip-output-port port
#:key
@@ -210,7 +194,7 @@ port is closed."
(define gzfile
(begin
(force-output port) ;empty PORT's buffer
- (gzdopen (fileno port)
+ (gzdopen (dup (fileno port))
(string-append "w" (number->string level)))))
(define (write! bv start count)
@@ -219,8 +203,10 @@ port is closed."
(unless (= buffer-size %default-buffer-size)
(gzbuffer! gzfile buffer-size))
+ (close-port port)
(make-custom-binary-output-port "gzip-output" write! #f #f
- (close-procedure gzfile port)))
+ (lambda ()
+ (gzclose gzfile))))
(define* (call-with-gzip-input-port port proc
#:key (buffer-size %default-buffer-size))