Package: guix-patches;
Reported by: ulfvonbelow <striness <at> tilde.club>
Date: Fri, 11 Aug 2023 09:05:02 UTC
Severity: normal
Tags: patch
Message #11 received at 65221 <at> debbugs.gnu.org (full text, mbox):
From: ulfvonbelow <striness <at> tilde.club> To: 65221 <at> debbugs.gnu.org Subject: [PATCH 2/2] service: use PRESERVE-PORTS for redirecting FDs 0-2. Date: Fri, 11 Aug 2023 04:06:15 -0500
There are currently some corner cases in how EXTRA-PORTS works due to it not
managing FDs 0, 1, and 2. Specifically, if one were to include a port in
EXTRA-PORTS with FD 0, 1, or 2, it would *not* be preserved, and would instead
represent the file that EXEC-COMMAND assigned to that file descriptor. To
avoid this, it's necessary to call PRESERVE-PORTS *before* redirecting the
input, but this could clobber LOG-PORT or INPUT-PORT, so it would become
necessary to include LOG-PORT and INPUT-PORT in the call to PRESERVE-PORTS,
then do the redirection using the new FD assignment, then close them. This
complication can be avoided if we simply let PRESERVE-PORTS itself do the
redirection. This also solves other edge cases, like if LOG-PORT has fileno 0
or 1 (previously passing a LOG-PORT of (current-output-port) would cause an
error, as the underlying file descriptor would be closed before dup2 was
called to copy it), or if INPUT-PORT has fileno 0.
To solve this, we modify PRESERVE-PORTS to allow both file descriptors and
ports, and to start the range it copies into at 0 instead of 3. We then
modify EXEC-COMMAND to explicitly pass the desired standard I/O FDs / ports at
the front of the list it passes to PRESERVE-PORTS.
* modules/shepherd/service.scm (preserve-ports): Allow elements of EXTRA-PORTS
to be either ports or file descriptors. Start the range of FDs being
duplicated into at 0 instead of 3.
(exec-command): use PRESERVE-PORTS for redirecting FDs 0, 1, and 2.
---
modules/shepherd/service.scm | 74 +++++++++++++++++-------------------
1 file changed, 35 insertions(+), 39 deletions(-)
diff --git a/modules/shepherd/service.scm b/modules/shepherd/service.scm
index ffbd03c..5f735fe 100644
--- a/modules/shepherd/service.scm
+++ b/modules/shepherd/service.scm
@@ -1435,10 +1435,10 @@ FILE."
supplementary-groups)))
(define (preserve-ports extra-ports)
- "Duplicate the FDs (fd1 fd2 ... fdN) corresponding to the N ports in
-EXTRA-PORTS into the FD range (3 4 ... 3+N). This will work regardless of the
+ "Duplicate the FDs (fd0 fd1 ... fdN) corresponding to the N+1 ports or FDs in
+EXTRA-PORTS into the FD range (0 1 ... N). This will work regardless of the
numeric values of fd1 ... fdN. Any open file descriptors not in EXTRA-PORTS
-and numbered 3 or higher WILL be closed or marked FD_CLOEXEC."
+WILL be closed or marked FD_CLOEXEC."
;; We employ the following strategy: copy FDs as high as possible, in
;; descending order of FD, so as to avoid clobbering, then copy the high FDs
;; to low FDs, in the order specified in EXTRA-PORTS. If more than half of
@@ -1449,8 +1449,9 @@ and numbered 3 or higher WILL be closed or marked FD_CLOEXEC."
(let* ((max-fds-count (max-file-descriptors))
(highest-fd (- max-fds-count 1))
(extra-fds-count (length extra-ports))
- (preserved-fds-count (+ 3 extra-fds-count))
- (extra-fds (map fileno extra-ports))
+ (extra-fds (map (lambda (x)
+ (if (port? x) (fileno x) x))
+ extra-ports))
(index+fd (map cons
(iota extra-fds-count)
extra-fds))
@@ -1470,15 +1471,15 @@ and numbered 3 or higher WILL be closed or marked FD_CLOEXEC."
(for-each (match-lambda
((by-fileno-index original-index . original-fd)
(dup2 (- highest-fd by-fileno-index)
- (+ 3 original-index))))
+ original-index)))
index2+fd)
(for-each (lambda (fd)
(catch-system-error
(let ((flags (fcntl fd F_GETFD)))
(when (zero? (logand flags FD_CLOEXEC))
(fcntl fd F_SETFD (logior FD_CLOEXEC flags))))))
- (iota (- max-fds-count preserved-fds-count)
- preserved-fds-count))))
+ (iota (- max-fds-count extra-fds-count)
+ extra-fds-count))))
(define* (exec-command command
#:key
@@ -1525,39 +1526,34 @@ false."
(chdir directory)
(environ environment-variables)
- ;; Redirect stdin.
- (catch-system-error (close-fdes 0))
- ;; Make sure file descriptor zero is used, so we don't end up reusing
- ;; it for something unrelated, which can confuse some packages.
- (dup2 (if input-port
- (fileno input-port)
- (open-fdes "/dev/null" O_RDONLY))
- 0)
-
- (when (or log-port log-file)
- (catch #t
- (lambda ()
- ;; Redirect stdout and stderr to use LOG-FILE.
- (catch-system-error (close-fdes 1))
- (catch-system-error (close-fdes 2))
- (dup2 (if log-file
- (open-fdes log-file (logior O_CREAT O_WRONLY O_APPEND)
- #o640)
- (fileno log-port))
- 1)
- (dup2 1 2))
-
- (lambda (key . args)
- (when log-file
- (format (current-error-port)
- "failed to open log-file ~s:~%" log-file))
- (print-exception (current-error-port) #f key args)
- (primitive-exit 1))))
-
- ;; Close all the file descriptors except stdout, stderr, and EXTRA-PORTS.
+ ;; Close all the file descriptors except stdin, stdout, stderr, and
+ ;; EXTRA-PORTS.
;; Make EXTRA-PORTS available starting from file descriptor 3.
;; This clears their FD_CLOEXEC flag.
- (preserve-ports extra-ports)
+ (let* ( ;; Make sure file descriptor zero is used, so we don't end up reusing
+ ;; it for something unrelated, which can confuse some packages.
+ (stdin (or input-port (open-fdes "/dev/null" O_RDONLY)))
+ (stdout (catch #t
+ (lambda ()
+ (or log-port
+ (and log-file
+ (open-fdes log-file
+ (logior O_CREAT O_WRONLY O_APPEND)
+ #o640))
+ 1))
+ (lambda (key . args)
+ (when log-file
+ (format (current-error-port)
+ "failed to open log-file ~s:~%" log-file))
+ (print-exception (current-error-port) #f key args)
+ (primitive-exit 1))))
+ (stderr (if (or log-port log-file)
+ stdout
+ 2)))
+ (preserve-ports (cons* stdin
+ stdout
+ stderr
+ extra-ports)))
;; setgid must be done *before* setuid, otherwise the user will
;; likely no longer have permissions to setgid.
--
2.40.1
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Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.