Segmentation fault on start

[jkobezda]

I'm getting segmentation faults when starting sway on a new Gentoo Hardened install using musl libc.

Sway output: https://0x0.st/MPr.txt

Dmesg: https://0x0.st/MPs.txt

[jkobezda]

(gdb) run -dV
Starting program: /usr/bin/sway -dV
08/19/16 09:52:01 - [wlc] Failed to create file for keymap

Program received signal SIGSEGV, Segmentation fault.
free (p=0x7f21953091c0) at src/malloc/malloc.c:464
464 src/malloc/malloc.c: No such file or directory.
(gdb) bt full
#0  free (p=0x7f21953091c0) at src/malloc/malloc.c:464
        self = 0x7f21953091b0
        next = 0x7f21953092b0
        final_size = 256
        new_size = 256
        size = <optimized out>
        reclaim = 0
#1  0x00007f2199162718 in xkb_keymap_unref () from /usr/lib/libxkbcommon.so.0
No symbol table info available.
#2  0x00007f21993974cc in wlc_keymap_release (keymap=keymap@entry=0x7f21995bc8e0 <wlc+544>)
    at /var/tmp/portage/dev-libs/wlc-9999/work/wlc-9999/src/compositor/seat/keymap.c:61
No locals.
#3  0x00007f2199399866 in wlc_seat_release (seat=0x7f21995bc6d8 <wlc+24>) at /var/tmp/portage/dev-libs/wlc-9999/work/wlc-9999/src/compositor/seat/seat.c:284
No locals.
#4  0x00007f2199399a22 in wlc_seat (seat=seat@entry=0x7f21995bc6d8 <wlc+24>)
    at /var/tmp/portage/dev-libs/wlc-9999/work/wlc-9999/src/compositor/seat/seat.c:331
        rules = {rules = 0x0, model = 0x0, layout = 0x0, variant = 0x0, options = 0x0}
#5  0x00007f21993921a5 in wlc_compositor (compositor=compositor@entry=0x7f21995bc6c0 <wlc>)
    at /var/tmp/portage/dev-libs/wlc-9999/work/wlc-9999/src/compositor/compositor.c:766
No locals.
#6  0x00007f21993aaa8c in wlc_init () at /var/tmp/portage/dev-libs/wlc-9999/work/wlc-9999/src/wlc.c:391
        x11display = 0x7ffeb39c4fb0 ":0"
        privileged = <optimized out>
        vt = <optimized out>
        socket_name = <optimized out>
        libinput = <optimized out>
#7  0x00005629867ad6ee in main (argc=2, argv=0x7ffeb39c4618) at /var/tmp/portage/dev-libs/sway-9999/work/sway-9999/sway/main.c:191
        verbose = 1
        debug = 1
        validate = 0
        long_options = {{name = 0x5629867d3f6f "help", has_arg = 0, flag = 0x0, val = 104}, {name = 0x5629867d26d8 "config", has_arg = 1, flag = 0x0, 
            val = 99}, {name = 0x5629867d3f74 "validate", has_arg = 0, flag = 0x0, val = 67}, {name = 0x5629867d3f7d "debug", has_arg = 0, flag = 0x0, 
            val = 100}, {name = 0x5629867d3f83 "version", has_arg = 0, flag = 0x0, val = 118}, {name = 0x5629867d35ca "verbose", has_arg = 0, flag = 0x0, 
            val = 86}, {name = 0x5629867d48af "get-socketpath", has_arg = 0, flag = 0x0, val = 112}, {name = 0x0, has_arg = 0, flag = 0x0, val = 0}}
        config_path = 0x0
        usage = 0x5629867d4098 "Usage: sway [options] [command]\n\n  -h, --help", ' ' <repeats 13 times>, "Show help message and quit.\n  -c, --config <config>  Specify a config file.\n  -C, --validate         Check the validity of the config file, th"...
        c = <optimized out>

[progandy]

That may be the result of a double free bug in wlc. It is called once inside of wlc_keymap in case of an error and once again during wlc_seat_release which is called after wlc_keymap fails

@Cloudef: Should wlc_keymap_release set the structure members to NULL? The alternative may be to do that each time after the wlc_keymap constructor fails.

[jkobezda]

So, the "Failed to create file for keymap" is because I had XDG_RUNTIME_DIR on a ZFS filesystem, which doesn't support fallocate(). See strace:

open("/tmp/john//wlc-shared-PeIHcJ", O_RDWR|O_CREAT|O_EXCL|O_CLOEXEC, 0600) = 10
fcntl(10, F_SETFD, FD_CLOEXEC)          = 0
unlink("/tmp/john//wlc-shared-PeIHcJ")  = 0
fallocate(10, 0, 0, 45094)              = -1 EOPNOTSUPP (Not supported)
close(10)                               = 0
open("/etc/localtime", O_RDONLY|O_NONBLOCK|O_CLOEXEC) = 10
fstat(10, {st_mode=S_IFREG|0644, st_size=2272, ...}) = 0
mmap(NULL, 2272, PROT_READ, MAP_SHARED, 10, 0) = 0x7f84f8cc2000
close(10)                               = 0
writev(2, [{"", 0}, {"08/19/16 15:12:40 - ", 20}], 208/19/16 15:12:40 - ) = 20
ioctl(2, TIOCGWINSZ, 0x7ffcad593100)    = -1 ENOTTY (Not a tty)
writev(2, [{"[wlc] Failed to create file for "..., 38}, {NULL, 0}], 2[wlc] Failed to create file for keymap) = 38
ioctl(2, TIOCGWINSZ, 0x7ffcad593100)    = -1 ENOTTY (Not a tty)
writev(2, [{"", 0}, {"\n", 1}], 2
)      = 1
--- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=0} ---
+++ killed by SIGSEGV +++
08/19/16 15:12:40 - [wlc] Parent exit (5926)

Edit: openzfs/zfs#326

[Cloudef]

@progandy Cloudef/wlc@fe0a704 Cloudef/wlc@fa780ce Yeah it should.

[Cloudef]

@jkobezda You could try compiling with -UHAVE_POSIX_FALLOCATE compiler flag to fall back to ftruncate.

[jkobezda]

I worked around it by putting XDG_RUNTIME_DIR on tmpfs.
Also it doesn't segfault anymore. Closing.