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Date:	Fri, 18 Oct 2024 07:08:06 +0900
To:	cygwin AT cygwin DOT com
Cc:	Christian Franke <Christian DOT Franke AT t-online DOT de>
Subject:	Re: cygwin 3.5.4-1: lockf() aborts on overlap and does not fail on
	overflow
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From:	Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Takashi Yano <yano AT tyan0 DOT yr32 DOT net>
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On Thu, 17 Oct 2024 18:37:57 +0200
Christian Franke wrote:
> Takashi Yano via Cygwin wrote:
> > On Mon, 14 Oct 2024 15:36:02 +0200
> > Christian Franke wrote:
> >> Two possibly independent bugs found by 'stress-ng --lockf ...':
> >>
> >> 1) lockf() may abort the process with api_fatal() if the new range
> >> partly overlaps with two ranges previously locked by the same process.
> >>
> >> 2) lockf() prints a warning on too many locks and returns success. It
> >> should not print a warning and fail with ENOLCK instead.
> >>
> >> Testcase for both:
> >>
> >> $ uname -r
> >> 3.5.4-1.x86_64
> >>
> >> $ cat locktest.c
> >> #include <fcntl.h>
> >> #include <stdio.h>
> >> #include <unistd.h>
> >>
> >> static int lock_at(int fd, int off, int size)
> >> {
> >>     if (lseek(fd, off, SEEK_SET) < 0) {
> >>       perror("lseek"); return -1;
> >>     }
> >>     printf("\rlock %d-%d\n", off, off + size - 1); fflush(stdout);
> >>     if (lockf(fd, F_LOCK, size) < 0) {
> >>       perror("lock"); return -1;
> >>     }
> >>     return 0;
> >> }
> >>
> >> int main(int argc, char **argv)
> >> {
> >>     int fd = open("locktest.tmp", O_RDWR|O_CREAT, 0666);
> >>     if (fd < 0) {
> >>       perror("open"); return 1;
> >>     }
> >>
> >>     if (argc == 1) {
> >>       lock_at(fd, 0, 2);
> >>       lock_at(fd, 2, 2);
> >>       lock_at(fd, 1, 2);
> >>     }
> >>     else {
> >>       for (int i = 0; i < 914; i++)
> >>         if (lock_at(fd, i, 1))
> >>           return 1;
> >>     }
> >>     printf("\rdone\n");
> >>     return 0;
> >> }
> >>
> >> $ gcc -o locktest locktest.c
> >>
> >> $ ./locktest
> >> lock 0-1
> >> lock 2-3
> >> lock 1-2
> >>        1 [main] locktest 44864 C:\cygwin64\tmp\locktest.exe: \
> >>          *** fatal error - NtCreateEvent(lock): 0xC0000035\
> >>          Hangup
> >>
> >> $ ./locktest loop
> >> lock 0-0
> >> lock 1-1
> >> lock 2-2
> >> lock 3-3
> >> ...
> >> lock 909-909
> >> lock 910-910
> >> lock 911-911
> >>         0 [main] locktest 44865 inode_t::get_all_locks_list: \
> >>           Warning, can't handle more than 910 locks per file.
> >> lock 912-912
> >>       727 [main] locktest 44865 inode_t::get_all_locks_list: \
> >>           Warning, can't handle more than 910 locks per file.
> >> lock 913-913
> >>      1329 [main] locktest 44865 inode_t::get_all_locks_list: \
> >>           Warning, can't handle more than 910 locks per file.
> >> done
> >>
> >> There is possibly also an off-by-one error as the 912'th lockf() prints
> >> the first warning.
> > Thanks for the report.
> > I looked into the problems, and considered how to fix them.
> >
> > Could you please try the experimental patch attached?
> 
> 
> Works as expected with both 'locktest.exe' and 'stress-ng --lockf ...'.

Thanks for testing!

-- 
Takashi Yano <yano AT tyan0 DOT yr32 DOT net>

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