[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
The following issue has a resolution that has been APPLIED. == https://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: Applied Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text:https://austingroupbugs.net/view.php?id=1318#c4797 Resolution: Accepted As Marked Fixed in Version: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-05-13 15:31 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support related to 0001337 Clarify socket option values after acce... related to 0001317 Require fork handlers to be called in c... == Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 2020-01-13 16:38 eblake Note Added: 0004728 2020-03-05 17:30 eblake Relationship added related to 0001317 2020-03-16 16:24 geoffclare Note Added: 0004797 2020-03-16 16:31 geoffclare Note Edited: 0004797 2020-03-16 16:33 geoffclare Interp Status => --- 2020-03-16 16:33 geoffclare Final Accepted Text => https://austingroupbugs.net/view.php?id=1318#c4797 2020-03-16 16:33 geoffclare Status New => Resolved 2020-03-16 16:33 geoffclare Resolution Open => Accepted As Marked 2020-03-16 16:33 geoffclare Tag Attached: issue8 2020-03-19 15:21 geoffclare Note Edited: 0004797 2020-03-26 15:29 geoffclare Note Edited: 0004797 2020-03-26 15:30 geoffclare Note Edited: 0004797 2020-03-26 15:32 geoffclare Note Added: 0004802 2020-04-29 17:43 eblake Relationship added related to 0001337 2020-05-13 15:31 geoffclare Status Resolved => Applied ==
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
A NOTE has been added to this issue. == https://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: Resolved Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text:https://austingroupbugs.net/view.php?id=1318#c4797 Resolution: Accepted As Marked Fixed in Version: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-03-26 15:32 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support related to 0001317 Require fork handlers to be called in c... == -- (0004802) geoffclare (manager) - 2020-03-26 15:32 https://austingroupbugs.net/view.php?id=1318#c4802 -- In the March 26, 2020 teleconference https://austingroupbugs.net/view.php?id=1318#c4797 was updated with further changes for accept(). Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 2020-01-13 16:38 eblake Note Added: 0004728 2020-03-05 17:30 eblake Relationship added related to 0001317 2020-03-16 16:24 geoffclare Note Added: 0004797 2020-03-16 16:31 geoffclare Note Edited: 0004797 2020-03-16 16:33 geoffclare Interp Status => --- 2020-03-16 16:33 geoffclare Final Accepted Text => https://austingroupbugs.net/view.php?id=1318#c4797 2020-03-16 16:33 geoffclare Status New => Resolved 2020-03-16 16:33 geoffclare Resolution Open => Accepted As Marked 2020-03-16 16:33 geoffclare Tag Attached: issue8 2020-03-19 15:21 geoffclare Note Edited: 0004797 2020-03-26 15:29 geoffclare Note Edited: 0004797 2020-03-26 15:30 geoffclare Note Edited: 0004797 2020-03-26 15:32 geoffclare Note Added: 0004802 ==
Re: [1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
casper@oracle.com wrote, on 17 Mar 2020: > > It seems that this bug changes the following commands about a "wf" or "rf" > option for popen(); however, I do not see the additional changes needed > for fopen(). It doesn't make any requirement for popen() to support "wf", it just encourages (in non-normative text) implementations to add it. It was done this way because it's invention. Applications can easily arrange for FD_CLOFORK to be set on a stream by using open() with O_CLOFORK and then fdopen(), instead of using fopen(). Doing the equivalent of popen() "wf" with lower-level calls is much harder. So we thought encouraging fopen() "wf" was not justified, but for popen() it is. Of course, implementations that add "wf" for popen() may want to add it to fopen() for consistency (and maybe also "rf" there, but a proper "rf" for popen() is very hard to implement). Maybe for Issue 9 there will be enough existing practice to standardise some of this. > Another question I have is this: in fdopen(), Solaris will NOT change the > file flags even when "e" is given; this makes sense, I think. The resolution of bug 411 currently requires fdopen() with "e" to set FD_CLOEXEC. (Without "e" it is required not to change it.) If specifying "e" does nothing, then there's no point requiring fdopen() to accept "e". > > So we ignore "e" on fdopen and would do the same for "f"; and I'm assuming > that the future standard will include "f" as the "open the file with > O_CLOFORK" for fopen() and ilk? We have no plans to require anything to do with "f" flags in Issue 8. As I said above, they may be candidates for standardising in Issue 9, but that will depend on what implementations do. -- Geoff Clare The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England
Re: [1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
It seems that this bug changes the following commands about a "wf" or "rf" option for popen(); however, I do not see the additional changes needed for fopen(). Another question I have is this: in fdopen(), Solaris will NOT change the file flags even when "e" is given; this makes sense, I think. So we ignore "e" on fdopen and would do the same for "f"; and I'm assuming that the future standard will include "f" as the "open the file with O_CLOFORK" for fopen() and ilk? Casper On page 1439 line 47807 section popen(), after the bug 411 text: ... any application worried about the potential file descriptor leak will already be using the e modifier. add a new paragraph: Implementations are encouraged to add support for a "wf" mode which creates the pipe as if by calling pipe2() with the O_CLOFORK flag and then clearing FD_CLOFORK for the read side of the pipe. This prevents the write side from leaking into child processes created by other threads, ensuring the child created by popen() will get end-of-file when the parent closes the write side (although the read side can still be leaked). Unfortunately there is no way (short of temporarily preventing other threads from creating child processes, or implementing an atomic create-pipe-and-fork system call) to implement an "rf" mode with the equivalent guarantee that the child created by popen() will be the only writer. Therefore multi-threaded applications that do not have complete control over process creation cannot rely on getting end-of-file on the stream and need to use an alternative method of indicating the end of communications.
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
The following issue has been RESOLVED. == https://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: Resolved Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text:https://austingroupbugs.net/view.php?id=1318#c4797 Resolution: Accepted As Marked Fixed in Version: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-03-16 16:33 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support related to 0001317 Require fork handlers to be called in c... == Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 2020-01-13 16:38 eblake Note Added: 0004728 2020-03-05 17:30 eblake Relationship added related to 0001317 2020-03-16 16:24 geoffclare Note Added: 0004797 2020-03-16 16:31 geoffclare Note Edited: 0004797 2020-03-16 16:33 geoffclare Interp Status => --- 2020-03-16 16:33 geoffclare Final Accepted Text => https://austingroupbugs.net/view.php?id=1318#c4797 2020-03-16 16:33 geoffclare Status New => Resolved 2020-03-16 16:33 geoffclare Resolution Open => Accepted As Marked ==
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
A NOTE has been added to this issue. == https://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: New Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-03-16 16:24 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support related to 0001317 Require fork handlers to be called in c... == -- (0004797) geoffclare (manager) - 2020-03-16 16:24 https://austingroupbugs.net/view.php?id=1318#c4797 -- On page 238 line 8018 section , change:The header shall define the following symbolic constant used for the fcntl() file descriptor flags, which shall be suitable for use in #if preprocessing directives. FD_CLOEXECClose the file descriptor upon execution of an exec family function.to:The header shall define the following symbolic constants used for the fcntl() file descriptor flags. The values shall be bitwise-distinct and shall be suitable for use in #if preprocessing directives. FD_CLOEXECClose the file descriptor upon successful execution of an exec family function [SPN]and in the new process image created by posix_spawn() or posix_spawnp()[/SPN]. FD_CLOFORKClose the file descriptor in any child process created from a process that has the file descriptor open; that is, the child shall not inherit the file descriptor. On page 238 line 8032 section , change:O_CLOEXECThe FD_CLOEXEC flag associated with the new descriptor shall be set to close the file descriptor upon execution of an exec family function.to:O_CLOEXECAtomically set the FD_CLOEXEC flag on the new file descriptor. O_CLOFORKAtomically set the FD_CLOFORK flag on the new file descriptor. On page 387 line 13167 section , after the bug 411 text:SOCK_CLOEXECCreate a socket file descriptor with the FD_CLOEXEC flag atomically set on that file descriptor.add:SOCK_CLOFORKCreate a socket file descriptor with the FD_CLOFORK flag atomically set on that file descriptor. On page 388 line 13195 section , after the bug 411 text:MSG_CMSG_CLOEXECAtomically set the FD_CLOEXEC flag on any file descriptors created via SCM_RIGHTS during recvmsg().add:MSG_CMSG_CLOFORKAtomically set the FD_CLOFORK flag on any file descriptors created via SCM_RIGHTS during recvmsg(). On page 497 line 17263 section 2.5.1, change:A file descriptor is closed by close(), _exit(), or the exec functions when FD_CLOEXEC is set on that file descriptor.to:Several functions close file descriptors, including close(), dup2(), _exit(), the exec functions when FD_CLOEXEC is set on a file descriptor, fork() when FD_CLOFORK is set on a file descriptor, and posix_spawn() when either FD_CLOEXEC or FD_CLOFORK is set. On page 568 line 19882 section accept(), after the bug 411 text:SOCK_CLOEXECAtomically set the FD_CLOEXEC flag on the new file descriptor.add:SOCK_CLOFORKAtomically set the FD_CLOFORK flag on the new file descriptor. On page 569 line 19914 section accept(), after applying bug 411 change:The SOCK_CLOEXEC flag of accept4() is necessary to avoid a data race in multi-threaded applications. Without it, a file descriptor is leaked into a child process created by one thread in the window between another thread creating a file descriptor with accept() and then using fcntl() to set the FD_CLOEXEC flag.to:The SOCK_CLOEXEC and SOCK_CLOFORK flags of accept4() are necessary to avoid a data race in multi-threaded applications. Without SOCK_CLOFORK, a file descriptor is leaked into a child process created by one thread in the window between another thread creating a file descriptor with accept() and then using fcntl() to set the FD_CLOFORK flag. Without
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
The following issue has been set as RELATED TO issue 0001317. == https://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: New Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-01-13 16:38 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support related to 0001317 Require fork handlers to be called in c... == Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 2020-01-13 16:38 eblake Note Added: 0004728 2020-03-05 17:30 eblake Relationship added related to 0001317 ==
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
A NOTE has been added to this issue. == http://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: New Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-01-13 16:38 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support == -- (0004728) eblake (manager) - 2020-01-13 16:38 http://austingroupbugs.net/view.php?id=1318#c4728 -- Standardization of dup3() and SOCK_CLOEXEC is already the subject of http://austingroupbugs.net/view.php?id=411 Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 2020-01-13 16:38 eblake Note Added: 0004728 ==
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
The following issue has been set as RELATED TO issue 411. == http://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: New Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-01-13 16:37 UTC == Summary:Define close-on-fork flag == Relationships ID Summary -- related to 411 adding atomic FD_CLOEXEC support == Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown 2020-01-13 07:28 kreNote Added: 0004725 2020-01-13 16:37 eblake Relationship added related to 411 ==
[1003.1(2016)/Issue7+TC2 0001318]: Define close-on-fork flag
The following issue has been SUBMITTED. == http://austingroupbugs.net/view.php?id=1318 == Reported By:nate_karstens Assigned To: == Project:1003.1(2016)/Issue7+TC2 Issue ID: 1318 Category: System Interfaces Type: Enhancement Request Severity: Comment Priority: normal Status: New Name: Nate Karstens Organization: Garmin User Reference: Section:fcntl, open, socket Page Number:Unknown Line Number:Unknown Interp Status: --- Final Accepted Text: == Date Submitted: 2020-01-12 10:50 UTC Last Modified: 2020-01-12 10:50 UTC == Summary:Define close-on-fork flag Description: Certain interfaces (like system(), popen(), etc.) are non-atomic in that their implementation first calls a fork() and then an exec(). This creates a race condition in certain scenarios. Please see https://www.mail-archive.com/austin-group-l@opengroup.org/msg05324.html and resulting discussion for a description of one such condition. Issue 1317 already requests enhancements to these interfaces, but this particular issue would also be solvable if there was a close-on-fork flag (similar to close-on-exec, but the file descriptor is closed in the child process after a fork). Desired Action: Add the following to fcntl()/F_DUPFD: The FD_CLOFORK flag associated with the new file descriptor shall be cleared to keep the file open in the child process after a fork. Add the following to fcntl()/F_SETFD If the FD_CLOFORK flag in the third argument is 0, the file descriptor shall remain open in the child process after a fork(). Otherwise, the file descriptor shall be closed in the child process after a fork(). Add the following to fcntl(): F_DUPFD_CLOFORK Like F_DUPFD, but the FD_CLOFORK flag associated with the new file descriptor shall be set. Additional changes to the RETURN VALUE and ERRORS sections may be necessary as well. Add the following to open(): O_CLOFORK If set, the FD_CLOFORK flag for the new file descriptor shall be set. POSIX does not currently specify SOCK_CLOEXEC, but this would be a useful addition. Add the following to socket(): SOCK_CLOEXEC If set, the close-on-exec (FD_CLOEXEC) flag for the new file descriptor shall be set. SOCK_CLOFORK If set, the close-on-fork (FD_CLOFORK) flag for the new file descriptor shall be set. In hindsight, it seems like it would have been preferable to have the default behavior be to close all file descriptors when the process forks, and have flags to override that behavior on an individual basis. Submitter cannot think of a way to do that and maintain backwards-compatibility, short of defining new system calls, but the idea seems like it would be worth considering. == Issue History Date ModifiedUsername FieldChange == 2020-01-12 10:50 nate_karstens New Issue 2020-01-12 10:50 nate_karstens Name => Nate Karstens 2020-01-12 10:50 nate_karstens Organization => Garmin 2020-01-12 10:50 nate_karstens Section => fcntl, open, socket 2020-01-12 10:50 nate_karstens Page Number => Unknown 2020-01-12 10:50 nate_karstens Line Number => Unknown ==
