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openSUSE:Leap:15.5:Update
libnbd.23097
794c8ce0-copy-dummy-vs-errno.patch
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File 794c8ce0-copy-dummy-vs-errno.patch of Package libnbd.23097
commit 794c8ce06e995ebd282e8f2b9465a06140572112 Author: Eric Blake <eblake@redhat.com> Date: Thu Feb 3 14:25:57 2022 -0600 copy: Pass in dummy variable rather than &errno to callback In several places where asynch handlers manually call the provided nbd_completion_callback, the value of errno is indeterminate (for example, in file-ops.c:file_asynch_read(), the previous call to file_synch_read() already triggered exit() on error, but does not guarantee what is left in errno on success). As the callback should be paying attention to the value of *error (to be fixed in the next patch), we are better off ensuring that we pass in a pointer to a known-zero value. Besides, passing in &errno carries a risk that if the callback uses any other library function that alters errno prior to dereferncing *error, it will no longer see the value we passed in. Thus, it is easier to use a dummy variable on the stack than to mess around with errno and it's magic macro expansion into a thread-local storage location. Note that several callsites then check if the callback returned -1, and if so assume that the callback has caused errno to now have a sane value to pass on to perror. In theory, the fact that we are no longer passing in &errno means that if the callback assigns into *error but did not otherwise affect errno (a tenuous assumption, given our argument above that we could not even guarantee that the callback does not accidentally alter errno prior to reading *error), our perror call would no longer reflect the intended error value from the callback. But in practice, since the callback never actually returned -1, nor even assigned into *error, the call to perror is dead code; although I have chosen to defer that additional cleanup to the next patch. Message-Id: <20220203202558.203013-5-eblake@redhat.com> Acked-by: Richard W.M. Jones <rjones@redhat.com> Acked-by: Nir Soffer <nsoffer@redhat.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Index: libnbd-1.9.3/copy/file-ops.c =================================================================== --- libnbd-1.9.3.orig/copy/file-ops.c +++ libnbd-1.9.3/copy/file-ops.c @@ -1,5 +1,5 @@ /* NBD client library in userspace. - * Copyright (C) 2020 Red Hat Inc. + * Copyright (C) 2020-2022 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -587,10 +587,11 @@ file_asynch_read (struct rw *rw, struct command *command, nbd_completion_callback cb) { + int dummy = 0; + file_synch_read (rw, slice_ptr (command->slice), command->slice.len, command->offset); - errno = 0; - if (cb.callback (cb.user_data, &errno) == -1) { + if (cb.callback (cb.user_data, &dummy) == -1) { perror (rw->name); exit (EXIT_FAILURE); } @@ -601,10 +602,11 @@ file_asynch_write (struct rw *rw, struct command *command, nbd_completion_callback cb) { + int dummy = 0; + file_synch_write (rw, slice_ptr (command->slice), command->slice.len, command->offset); - errno = 0; - if (cb.callback (cb.user_data, &errno) == -1) { + if (cb.callback (cb.user_data, &dummy) == -1) { perror (rw->name); exit (EXIT_FAILURE); } @@ -614,10 +616,11 @@ static bool file_asynch_zero (struct rw *rw, struct command *command, nbd_completion_callback cb, bool allocate) { + int dummy = 0; + if (!file_synch_zero (rw, command->offset, command->slice.len, allocate)) return false; - errno = 0; - if (cb.callback (cb.user_data, &errno) == -1) { + if (cb.callback (cb.user_data, &dummy) == -1) { perror (rw->name); exit (EXIT_FAILURE); } Index: libnbd-1.9.3/copy/multi-thread-copying.c =================================================================== --- libnbd-1.9.3.orig/copy/multi-thread-copying.c +++ libnbd-1.9.3/copy/multi-thread-copying.c @@ -1,5 +1,5 @@ /* NBD client library in userspace. - * Copyright (C) 2020 Red Hat Inc. + * Copyright (C) 2020-2022 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -393,6 +393,7 @@ finished_read (void *vp, int *error) bool last_is_hole = false; uint64_t i; struct command *newcommand; + int dummy = 0; /* Iterate over whole blocks in the command, starting on a block * boundary. @@ -475,7 +476,7 @@ finished_read (void *vp, int *error) /* Free the original command since it has been split into * subcommands and the original is no longer needed. */ - free_command (command, &errno); + free_command (command, &dummy); } return 1; /* auto-retires the command */ @@ -502,6 +503,7 @@ fill_dst_range_with_zeroes (struct comma { char *data; size_t data_size; + int dummy = 0; if (destination_is_zero) goto free_and_return; @@ -537,7 +539,7 @@ fill_dst_range_with_zeroes (struct comma free (data); free_and_return: - free_command (command, &errno); + free_command (command, &dummy); } static int Index: libnbd-1.9.3/copy/null-ops.c =================================================================== --- libnbd-1.9.3.orig/copy/null-ops.c +++ libnbd-1.9.3/copy/null-ops.c @@ -1,5 +1,5 @@ /* NBD client library in userspace. - * Copyright (C) 2020-2021 Red Hat Inc. + * Copyright (C) 2020-2022 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -117,8 +117,9 @@ null_asynch_write (struct rw *rw, struct command *command, nbd_completion_callback cb) { - errno = 0; - if (cb.callback (cb.user_data, &errno) == -1) { + int dummy = 0; + + if (cb.callback (cb.user_data, &dummy) == -1) { perror (rw->name); exit (EXIT_FAILURE); } @@ -128,8 +129,9 @@ static bool null_asynch_zero (struct rw *rw, struct command *command, nbd_completion_callback cb, bool allocate) { - errno = 0; - if (cb.callback (cb.user_data, &errno) == -1) { + int dummy = 0; + + if (cb.callback (cb.user_data, &dummy) == -1) { perror (rw->name); exit (EXIT_FAILURE); }
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