GNU bug report logs - #39948
28.0.50; crash in fchmodat

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Package: emacs;

Reported by: Stephen Berman <stephen.berman <at> gmx.net>

Date: Fri, 6 Mar 2020 14:17:01 UTC

Severity: normal

Found in version 28.0.50

Done: Stephen Berman <stephen.berman <at> gmx.net>

Bug is archived. No further changes may be made.

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Message #17 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 39948 <at> debbugs.gnu.org, Stephen Berman <stephen.berman <at> gmx.net>,
 Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 17:45:49 +0100

>>>>> On Fri, 06 Mar 2020 17:45:13 +0200, Eli Zaretskii <eliz <at> gnu.org> said:

    >> From: Stephen Berman <stephen.berman <at> gmx.net>
    >> Date: Fri, 06 Mar 2020 15:16:43 +0100
    >> 
    >> I updated from master today and now Emacs is crashing when I use Gnus.
    >> The first time it happened I been reading news groups for a while, then
    >> email arrived and when I pulled it into Gnus, Emacs crashed.  Then I
    >> restarted Emacs under GDB and now get the crash already on starting Gnus
    >> (with my initializations; it doesn't happen when I start an unconfigured
    >> Gnus in Emacs -Q).  I tried to get a full backtrace, but the output of
    >> `bt full' seemed to be in an endless loop; here's the start of the
    >> backtrace:
    >> 
    >> Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
    >> 0x000000000060c9b2 in fchmodat (dir=dir <at> entry=-100,
    >> file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov",
    >> mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
    >> 65      {
    >> (gdb) bt full
    >> #0  0x000000000060c9b2 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
    >> #1  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
    >> #2  0x000000000060c9e0 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
    >> #3  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
    >> #4  0x000000000060c9e0 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
    >> #5  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> ter/lib/fchmodat.c:33
    >> 
    >> This pattern repeated for tens of thousands of frames, then I
    >> interrupted it and typed `c':

    Eli> Sounds like infinite recursion, which causes stack overflow.

lib/fchmodat.c:fchmodat can call lib/fchmodat.c:orig_fchmodat, which
can call fchmodat. Presumably that last one is meant to be the system
fchmodat, but itʼs calling the fchmodat.c:fchmodat one instead. CC'ing
Paul.

Robert
This bug report was last modified 5 years and 72 days ago.

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