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fix tail on kernels with 64k page size

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Resolves: RHEL-22866
This commit is contained in:
Lukáš Zaoral 2024-01-29 13:30:32 +01:00
parent 35b70e7b54
commit a5b35b6413
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GPG Key ID: 39157506DD67752D
2 changed files with 211 additions and 1 deletions
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204
coreutils-8.32-tail-64kpages.patch Normal file
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@ -0,0 +1,204 @@
From 73d119f4f8052a9fb6cef13cd9e75d5a4e23311a Mon Sep 17 00:00:00 2001
From: dann frazier <dann.frazier@canonical.com>
Date: Wed, 29 Nov 2023 18:32:34 -0700
Subject: [PATCH] tail: fix tailing sysfs files where PAGE_SIZE > BUFSIZ
* src/tail.c (file_lines): Ensure we use a buffer size >= PAGE_SIZE when
searching backwards to avoid seeking within a file,
which on sysfs files is accepted but also returns no data.
* tests/tail/tail-sysfs.sh: Add a new test.
* tests/local.mk: Reference the new test.
Fixes https://bugs.gnu.org/67490
Upstream-commit: 73d119f4f8052a9fb6cef13cd9e75d5a4e23311a
Cherry-picked-by: Lukáš Zaoral <lzaoral@redhat.com>
---
src/tail.c | 57 +++++++++++++++++++++++++++++-----------
tests/local.mk | 1 +
tests/tail-2/tail-sysfs.sh | 34 ++++++++++++++++++++++++
3 files changed, 77 insertions(+), 15 deletions(-)
create mode 100755 tests/tail/tail-sysfs.sh
diff --git a/src/tail.c b/src/tail.c
index c45f3b65a..6979e0ba3 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -208,6 +208,9 @@ static int nbpids = 0;
that is writing to all followed files. */
static pid_t pid;
+/* Used to determine the buffer size when scanning backwards in a file. */
+static int page_size;
+
/* True if we have ever read standard input. */
static bool have_read_stdin;
@@ -515,22 +518,40 @@ xlseek (int fd, off_t offset, int whence, char const *filename)
Return true if successful. */
static bool
-file_lines (const char *pretty_filename, int fd, uintmax_t n_lines,
- off_t start_pos, off_t end_pos, uintmax_t *read_pos)
+file_lines (const char *pretty_filename, int fd, struct stat const *sb,
+ uintmax_t n_lines, off_t start_pos, off_t end_pos,
+ uintmax_t *read_pos)
{
- char buffer[BUFSIZ];
+ char *buffer;
size_t bytes_read;
+ blksize_t bufsize = BUFSIZ;
off_t pos = end_pos;
+ bool ok = true;
if (n_lines == 0)
return true;
+ /* Be careful with files with sizes that are a multiple of the page size,
+ as on /proc or /sys file systems these files accept seeking to within
+ the file, but then return no data when read. So use a buffer that's
+ at least PAGE_SIZE to avoid seeking within such files.
+
+ We could also indirectly use a large enough buffer through io_blksize()
+ however this would be less efficient in the common case, as it would
+ generally pick a larger buffer size, resulting in reading more data
+ from the end of the file. */
+ assert (S_ISREG (sb->st_mode));
+ if (sb->st_size % page_size == 0)
+ bufsize = MAX (BUFSIZ, page_size);
+
+ buffer = xmalloc (bufsize);
+
/* Set 'bytes_read' to the size of the last, probably partial, buffer;
- 0 < 'bytes_read' <= 'BUFSIZ'. */
- bytes_read = (pos - start_pos) % BUFSIZ;
+ 0 < 'bytes_read' <= 'bufsize'. */
+ bytes_read = (pos - start_pos) % bufsize;
if (bytes_read == 0)
- bytes_read = BUFSIZ;
- /* Make 'pos' a multiple of 'BUFSIZ' (0 if the file is short), so that all
+ bytes_read = bufsize;
+ /* Make 'pos' a multiple of 'bufsize' (0 if the file is short), so that all
reads will be on block boundaries, which might increase efficiency. */
pos -= bytes_read;
xlseek (fd, pos, SEEK_SET, pretty_filename);
@@ -538,7 +559,8 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
if (bytes_read == SAFE_READ_ERROR)
{
error (0, errno, _("error reading %s"), quoteaf (pretty_filename));
- return false;
+ ok = false;
+ goto free_buffer;
}
*read_pos = pos + bytes_read;
@@ -565,7 +587,7 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
xwrite_stdout (nl + 1, bytes_read - (n + 1));
*read_pos += dump_remainder (false, pretty_filename, fd,
end_pos - (pos + bytes_read));
- return true;
+ goto free_buffer;
}
}
@@ -577,23 +599,26 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
xlseek (fd, start_pos, SEEK_SET, pretty_filename);
*read_pos = start_pos + dump_remainder (false, pretty_filename, fd,
end_pos);
- return true;
+ goto free_buffer;
}
- pos -= BUFSIZ;
+ pos -= bufsize;
xlseek (fd, pos, SEEK_SET, pretty_filename);
- bytes_read = safe_read (fd, buffer, BUFSIZ);
+ bytes_read = safe_read (fd, buffer, bufsize);
if (bytes_read == SAFE_READ_ERROR)
{
error (0, errno, _("error reading %s"), quoteaf (pretty_filename));
- return false;
+ ok = false;
+ goto free_buffer;
}
*read_pos = pos + bytes_read;
}
while (bytes_read > 0);
- return true;
+free_buffer:
+ free (buffer);
+ return ok;
}
/* Print the last N_LINES lines from the end of the standard input,
@@ -1915,7 +1940,7 @@ tail_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
{
*read_pos = end_pos;
if (end_pos != 0
- && ! file_lines (pretty_filename, fd, n_lines,
+ && ! file_lines (pretty_filename, fd, &stats, n_lines,
start_pos, end_pos, read_pos))
return false;
}
@@ -2337,6 +2362,8 @@ main (int argc, char **argv)
atexit (close_stdout);
+ page_size = getpagesize ();
+
have_read_stdin = false;
count_lines = true;
diff --git a/tests/local.mk b/tests/local.mk
index db4ee7ed8..bf03238c3 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -257,6 +257,7 @@ all_tests = \
tests/misc/seq-precision.sh \
tests/misc/head.pl \
tests/misc/head-elide-tail.pl \
+ tests/tail-2/tail-sysfs.sh \
tests/tail-2/tail-n0f.sh \
tests/misc/ls-misc.pl \
tests/misc/date.pl \
diff --git a/tests/tail/tail-sysfs.sh b/tests/tail-2/tail-sysfs.sh
new file mode 100755
index 000000000..00874b3dc
--- /dev/null
+++ b/tests/tail-2/tail-sysfs.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+# sysfs files have weird properties that can be influenced by page size
+
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ tail
+
+file='/sys/kernel/profiling'
+
+test -r "$file" || skip_ "No $file file"
+
+cp -f "$file" exp || framework_failure_
+
+tail -n1 "$file" > out || fail=1
+compare exp out || fail=1
+
+tail -c2 "$file" > out || fail=1
+compare exp out || fail=1
+
+Exit $fail

8
coreutils.spec
View File

@ -1,7 +1,7 @@
Summary: A set of basic GNU tools commonly used in shell scripts
Name: coreutils
Version: 8.32
Release: 34%{?dist}
Release: 35%{?dist}
License: GPLv3+
Url: https://www.gnu.org/software/coreutils/
Source0: https://ftp.gnu.org/gnu/%{name}/%{name}-%{version}.tar.xz
@ -70,6 +70,9 @@ Patch18: coreutils-9.0-autofs-no-mount.patch
# basic support for checking NFSv4 ACLs (#2137866)
Patch19: coreutils-nfsv4-acls.patch
# fix tail on kernels with 64k pagesize
Patch20: coreutils-8.32-tail-64kpages.patch
# disable the test-lock gnulib test prone to deadlock
Patch100: coreutils-8.26-test-lock.patch
@ -324,6 +327,9 @@ rm -f $RPM_BUILD_ROOT%{_infodir}/dir
%license COPYING
%changelog
* Mon Jan 29 2024 Lukáš Zaoral <lzaoral@redhat.com>
- fix tail on kernels with 64k page sizes (RHEL-22866)
* Mon Jan 02 2023 Kamil Dudka <kdudka@redhat.com> - 8.32-34
- basic support for checking NFSv4 ACLs (#2137866)