111 lines
3.4 KiB
Diff
111 lines
3.4 KiB
Diff
commit 3ff3b9997cfef891ba33a14f1dcba0310d96369c
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Author: Joseph Myers <josmyers@redhat.com>
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Date: Tue Jan 28 23:20:08 2025 +0000
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Fix fflush handling for mmap files after ungetc (bug 32535)
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As discussed in bug 32535, fflush fails on files opened for reading
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using mmap after ungetc. Fix the logic to handle this case and still
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compute the file offset correctly.
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Tested for x86_64.
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diff --git a/libio/fileops.c b/libio/fileops.c
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index e3967c1eb8ee6993..ac5ff9a4353d0201 100644
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--- a/libio/fileops.c
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+++ b/libio/fileops.c
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@@ -858,17 +858,21 @@ libc_hidden_ver (_IO_new_file_sync, _IO_file_sync)
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int
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_IO_file_sync_mmap (FILE *fp)
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{
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+ off64_t o = fp->_offset - (fp->_IO_read_end - fp->_IO_read_ptr);
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if (fp->_IO_read_ptr != fp->_IO_read_end)
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{
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- if (__lseek64 (fp->_fileno, fp->_IO_read_ptr - fp->_IO_buf_base,
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- SEEK_SET)
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- != fp->_IO_read_ptr - fp->_IO_buf_base)
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+ if (_IO_in_backup (fp))
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+ {
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+ _IO_switch_to_main_get_area (fp);
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+ o -= fp->_IO_read_end - fp->_IO_read_base;
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+ }
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+ if (__lseek64 (fp->_fileno, o, SEEK_SET) != o)
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{
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fp->_flags |= _IO_ERR_SEEN;
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return EOF;
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}
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}
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- fp->_offset = fp->_IO_read_ptr - fp->_IO_buf_base;
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+ fp->_offset = o;
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fp->_IO_read_end = fp->_IO_read_ptr = fp->_IO_read_base;
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return 0;
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}
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diff --git a/stdio-common/Makefile b/stdio-common/Makefile
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index 9a5d324495946385..710120820ee4e337 100644
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--- a/stdio-common/Makefile
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+++ b/stdio-common/Makefile
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@@ -211,6 +211,7 @@ tests := \
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tst-fdopen2 \
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tst-ferror \
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tst-fflush-all-input \
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+ tst-fflush-mmap \
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tst-fgets \
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tst-fgets2 \
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tst-fileno \
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diff --git a/stdio-common/tst-fflush-mmap.c b/stdio-common/tst-fflush-mmap.c
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new file mode 100644
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index 0000000000000000..3bddb909e072caf2
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--- /dev/null
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+++ b/stdio-common/tst-fflush-mmap.c
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@@ -0,0 +1,50 @@
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+/* Test fflush after ungetc on files using mmap (bug 32535).
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+ Copyright (C) 2025 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <stdio.h>
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+
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+#include <support/check.h>
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+#include <support/temp_file.h>
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+#include <support/xstdio.h>
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+#include <support/xunistd.h>
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+
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+int
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+do_test (void)
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+{
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+ char *filename = NULL;
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+ int fd = create_temp_file ("tst-fflush-mmap", &filename);
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+ TEST_VERIFY_EXIT (fd != -1);
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+ xclose (fd);
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+
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+ /* Test fflush after ungetc (bug 32535). */
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+ FILE *fp = xfopen (filename, "w");
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+ TEST_VERIFY (0 <= fputs ("test", fp));
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+ xfclose (fp);
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+
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+ fp = xfopen (filename, "rm");
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+ TEST_COMPARE (fgetc (fp), 't');
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+ TEST_COMPARE (ungetc ('u', fp), 'u');
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+ TEST_COMPARE (fflush (fp), 0);
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+ TEST_COMPARE (fgetc (fp), 't');
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+ TEST_COMPARE (fgetc (fp), 'e');
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+ xfclose (fp);
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+
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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