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chardev/parallel: Don't close stdin on inappropriate device

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The __linux__ version of qemu_chr_open_pp_fd() tries to claim the
parport device with a PPCLAIM ioctl().  On success, it stores the file
descriptor in the chardev object, and returns success.  On failure, it
closes the file descriptor, and returns failure.

chardev_new() then passes the Chardev to object_unref().  This duly
calls char_parallel_finalize(), which closes the file descriptor
stored in the chardev object.  Since qemu_chr_open_pp_fd() didn't
store it, it's still zero, so this closes standard input.  Ooopsie.

To demonstate, add a unit test.  With the bug above unfixed, running
this test closes standard input.  char_hotswap_test() happens to run
next.  It opens a socket, duly gets file descriptor 0, and since it
tests for success with > 0 instead of >= 0, it fails.

The new unit test needs to be conditional exactly like the chardev it
tests.  Since the condition is rather complicated, steal the solution
from the serial chardev: define HAVE_CHARDEV_PARALLEL in qemu/osdep.h.
This also permits simplifying chardev/meson.build a bit.

The bug fix is easy enough: store the file descriptor, and leave
closing it to char_parallel_finalize().

The next commit will fix char_hotswap_test()'s test for success.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240203080228.2766159-2-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[Test fixed up for BSDs, indentation fixed up, commit message improved]
This commit is contained in:
Markus Armbruster 2024-02-03 09:02:25 +01:00
parent 5d1fc61441
commit a58c439a2d
4 changed files with 41 additions and 6 deletions
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27
tests/unit/test-char.c
View file

@ -1203,6 +1203,30 @@ static void char_serial_test(void)
}
#endif
#if defined(HAVE_CHARDEV_PARALLEL) && !defined(WIN32)
static void char_parallel_test(void)
{
QemuOpts *opts;
Chardev *chr;
opts = qemu_opts_create(qemu_find_opts("chardev"), "parallel-id",
1, &error_abort);
qemu_opt_set(opts, "backend", "parallel", &error_abort);
qemu_opt_set(opts, "path", "/dev/null", &error_abort);
chr = qemu_chr_new_from_opts(opts, NULL, NULL);
#ifdef __linux__
/* fails to PPCLAIM, see qemu_chr_open_pp_fd() */
g_assert_null(chr);
#else
g_assert_nonnull(chr);
object_unparent(OBJECT(chr));
#endif
qemu_opts_del(opts);
}
#endif
#ifndef _WIN32
static void char_file_fifo_test(void)
{
@ -1544,6 +1568,9 @@ int main(int argc, char **argv)
g_test_add_func("/char/udp", char_udp_test);
#if defined(HAVE_CHARDEV_SERIAL) && !defined(WIN32)
g_test_add_func("/char/serial", char_serial_test);
#endif
#if defined(HAVE_CHARDEV_PARALLEL) && !defined(WIN32)
g_test_add_func("/char/parallel", char_parallel_test);
#endif
g_test_add_func("/char/hotswap", char_hotswap_test);
g_test_add_func("/char/websocket", char_websock_test);