523afc95f6
Backports: - tests: replace fread by xfread - Fix fflush after ungetc on input file (bug 5994) - Make fclose seek input file to right offset (bug 12724) - Make fflush (NULL) flush input files (bug 32369) - Fix fseek handling for mmap files after ungetc or fflush (bug 32529) - Fix fflush handling for mmap files after ungetc (bug 32535) - Add test of input file flushing / offset issues - libio: Synthesize ESPIPE error if lseek returns 0 after reading bytes Resolves: RHEL-68805
116 lines
3.7 KiB
Diff
116 lines
3.7 KiB
Diff
commit 0dcc0b2f63051863187dc678964eb17761b1a820
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Author: Joseph Myers <josmyers@redhat.com>
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Date: Tue Jan 28 22:35:21 2025 +0000
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Fix fseek handling for mmap files after ungetc or fflush (bug 32529)
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As discussed in bug 32529, fseek fails on files opened for reading
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using mmap after ungetc. The implementation of fseek for such files
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has an offset computation that's also incorrect after fflush. A
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combined fix addresses both problems (with tests for both included as
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well) and it seems reasonable to consider them a single bug.
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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 47e9b5c27a5bca9f..c77f3572ba23cb05 100644
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--- a/libio/fileops.c
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+++ b/libio/fileops.c
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@@ -1106,11 +1106,18 @@ _IO_file_seekoff_mmap (FILE *fp, off64_t offset, int dir, int mode)
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if (mode == 0)
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return fp->_offset - (fp->_IO_read_end - fp->_IO_read_ptr);
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+ if (_IO_in_backup (fp))
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+ {
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+ if (dir == _IO_seek_cur)
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+ offset += fp->_IO_read_ptr - fp->_IO_read_end;
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+ _IO_switch_to_main_get_area (fp);
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+ }
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+
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switch (dir)
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{
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case _IO_seek_cur:
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/* Adjust for read-ahead (bytes is buffer). */
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- offset += fp->_IO_read_ptr - fp->_IO_read_base;
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+ offset += fp->_offset - (fp->_IO_read_end - fp->_IO_read_ptr);
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break;
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case _IO_seek_set:
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break;
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diff --git a/stdio-common/Makefile b/stdio-common/Makefile
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index 0476c3777d7d21c4..c620d0ce3681a1ec 100644
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--- a/stdio-common/Makefile
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+++ b/stdio-common/Makefile
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@@ -246,6 +246,7 @@ tests := \
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tst-freopen64-6 \
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tst-freopen64-7 \
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tst-fseek \
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+ tst-fseek-mmap \
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tst-fwrite \
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tst-fwrite-memstrm \
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tst-fwrite-overflow \
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diff --git a/stdio-common/tst-fseek-mmap.c b/stdio-common/tst-fseek-mmap.c
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new file mode 100644
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index 0000000000000000..86fa99a1a2e3e7e9
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--- /dev/null
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+++ b/stdio-common/tst-fseek-mmap.c
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@@ -0,0 +1,59 @@
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+/* Test fseek on files using mmap (bug 32529).
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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-fseek-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 fseek after ungetc (bug 32529). */
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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 (fseek (fp, 0, SEEK_CUR), 0);
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+ xfclose (fp);
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+
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+ /* Test fseek positioning after fflush (another issue covered by the
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+ same fix). */
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+ fp = xfopen (filename, "rm");
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+ TEST_COMPARE (fgetc (fp), 't');
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+ TEST_COMPARE (fflush (fp), 0);
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+ TEST_COMPARE (ftell (fp), 1);
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+ TEST_COMPARE (fseek (fp, 0, SEEK_CUR), 0);
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+ TEST_COMPARE (ftell (fp), 1);
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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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