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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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9
include/qemu/osdep.h
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@ -508,11 +508,18 @@ void qemu_anon_ram_free(void *ptr, size_t size);
#ifdef _WIN32
#define HAVE_CHARDEV_SERIAL 1
#elif defined(__linux__) || defined(__sun__) || defined(__FreeBSD__) \
#define HAVE_CHARDEV_PARALLEL 1
#else
#if defined(__linux__) || defined(__sun__) || defined(__FreeBSD__) \
|| defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) \
|| defined(__GLIBC__) || defined(__APPLE__)
#define HAVE_CHARDEV_SERIAL 1
#endif
#if defined(__linux__) || defined(__FreeBSD__) \
|| defined(__FreeBSD_kernel__) || defined(__DragonFly__)
#define HAVE_CHARDEV_PARALLEL 1
#endif
#endif
#if defined(__HAIKU__)
#define SIGIO SIGPOLL