xl devd crashes in domU - Xen 4.20

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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Hi,

Driver domains do not work in Xen 4.20, due to `xl devd` crashing. I've
got a report about it in Debian 13, but I can reproduce the issue
outside of Debian too.

I can reproduce the issue on master too.

The original report: https://github.com/QubesOS/qubes-issues/issues/10050#issuecomment-3092559292
And analysis done there:

user@sys-whonix-firewall:~/xen-4.20.0+68-g35cb38b222$ gdb --args /usr/lib/xen-4.20/bin/xl devd
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Reading symbols from /usr/lib/xen-4.20/bin/xl...
Reading symbols from /usr/lib/debug/.build-id/e0/c4fd106db94ad95b556765d61df2ec13fe674e.debug...
(gdb) r
Starting program: /usr/lib/xen-4.20/bin/xl devd
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
__strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex-base.S:81
warning: 81     ../sysdeps/x86_64/multiarch/strlen-evex-base.S: No such file or directory
(gdb) bt
#0  __strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex-base.S:81
#1  0x00007ffff7d95d7b in __GI___regexec (preg=preg@entry=0x7fffffffdc50, string=0x0, nmatch=nmatch@entry=0, pmatch=pmatch@entry=0x0,
eflags=eflags@entry=0)
    at ./posix/regexec.c:211
#2  0x00007ffff7e013e9 in __compat_regexec (preg=preg@entry=0x7fffffffdc50, string=<optimized out>, nmatch=nmatch@entry=0, pmatch=pmatch@entry=0x0,
    eflags=eflags@entry=0) at ./posix/regexec.c:240
#3  0x00005555555610c1 in auto_autoballoon () at ./tools/xl/xl.c:96
#4  parse_global_config (configfile=0x55555557f0c3 "/etc/xen/xl.conf", configfile_data=<optimized out>, configfile_len=<optimized out>) at
./tools/xl/xl.c:134
#5  main (argc=2, argv=0x7fffffffdde8) at ./tools/xl/xl.c:436
(gdb) frame 3
#3  0x00005555555610c1 in auto_autoballoon () at ./tools/xl/xl.c:96
96          ret = regexec(&regex, info->commandline, 0, NULL, 0);
(gdb) list
91      #undef SIZE_PATTERN
92
93          if (ret)
94              return 1;
95
96          ret = regexec(&regex, info->commandline, 0, NULL, 0);
97          regfree(&regex);
98
99          return ret == REG_NOMATCH;
100     }
(gdb) print info->commandline
$1 = 0x0
(gdb)


-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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