--- /dev/null
+From 66be5a789e70f911170017754fc51e499998f90e Mon Sep 17 00:00:00 2001
+From: Paul Eggert <eggert@cs.ucla.edu>
+Date: Sun, 14 Aug 2022 16:32:26 -0700
+Subject: [PATCH] Avoid excess lseek etc.
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+* src/buffer.c, src/delete.c: Do not include system-ioctl.h.
+* src/buffer.c (guess_seekable_archive): Remove. This is now done
+by get_archive_status, in a different way.
+(get_archive_status): New function that gets archive_stat
+unless remote, and sets seekable_archive etc.
+(_open_archive): Prefer bool for boolean.
+(_open_archive, new_volume): Get archive status consistently
+by calling get_archive_status in both places.
+* src/buffer.c (backspace_output):
+* src/compare.c (verify_volume):
+* src/delete.c (move_archive):
+Let mtioseek worry about mtio.
+* src/common.h (archive_stat): New global, replacing ar_dev and
+ar_ino. All uses changed.
+* src/delete.c (move_archive): Check for integer overflow.
+Also report overflow if the archive position would go negative.
+* src/system.c: Include system-ioctl.h, for MTIOCTOP etc.
+(mtioseek): New function, which also checks for integer overflow.
+(sys_save_archive_dev_ino): Remove.
+(archive_stat): Now
+(sys_get_archive_stat): Also initialize mtioseekable_archive.
+(sys_file_is_archive): Don’t return true if the archive is /dev/null
+since it’s not a problem in that case.
+(sys_detect_dev_null_output): Cache dev_null_stat.
+
+doc: omit MS-DOS mentions in doc
+It’s really FAT32 we’re worried about now, not MS-DOS.
+And doschk is no longer a GNU program.
+---
+ src/buffer.c | 99 ++++++++++++++++++---------------------------------
+ src/common.h | 10 +++---
+ src/compare.c | 31 ++++------------
+ src/delete.c | 51 +++++++++-----------------
+ src/system.c | 81 +++++++++++++++++++++++++++--------------
+ 5 files changed, 119 insertions(+), 153 deletions(-)
+
+--- a/src/buffer.c
++++ b/src/buffer.c
+@@ -20,7 +20,6 @@
+ Written by John Gilmore, on 1985-08-25. */
+
+ #include <system.h>
+-#include <system-ioctl.h>
+
+ #include <signal.h>
+
+@@ -420,37 +419,6 @@ check_compressed_archive (bool *pshort)
+ return ct_none;
+ }
+
+-/* Guess if the archive is seekable. */
+-static void
+-guess_seekable_archive (void)
+-{
+- struct stat st;
+-
+- if (subcommand_option == DELETE_SUBCOMMAND)
+- {
+- /* The current code in delete.c is based on the assumption that
+- skip_member() reads all data from the archive. So, we should
+- make sure it won't use seeks. On the other hand, the same code
+- depends on the ability to backspace a record in the archive,
+- so setting seekable_archive to false is technically incorrect.
+- However, it is tested only in skip_member(), so it's not a
+- problem. */
+- seekable_archive = false;
+- }
+-
+- if (seek_option != -1)
+- {
+- seekable_archive = !!seek_option;
+- return;
+- }
+-
+- if (!multi_volume_option && !use_compress_program_option
+- && fstat (archive, &st) == 0)
+- seekable_archive = S_ISREG (st.st_mode);
+- else
+- seekable_archive = false;
+-}
+-
+ /* Open an archive named archive_name_array[0]. Detect if it is
+ a compressed archive of known type and use corresponding decompression
+ program if so */
+@@ -702,12 +670,41 @@ check_tty (enum access_mode mode)
+ }
+ }
+
++/* Fetch the status of the archive, accessed via WANTED_STATUS. */
++
++static void
++get_archive_status (enum access_mode wanted_access, bool backed_up_flag)
++{
++ if (!sys_get_archive_stat ())
++ {
++ int saved_errno = errno;
++
++ if (backed_up_flag)
++ undo_last_backup ();
++ errno = saved_errno;
++ open_fatal (archive_name_array[0]);
++ }
++
++ seekable_archive
++ = (! (multi_volume_option || use_compress_program_option)
++ && (seek_option < 0
++ ? (_isrmt (archive)
++ || S_ISREG (archive_stat.st_mode)
++ || S_ISBLK (archive_stat.st_mode))
++ : seek_option));
++
++ if (wanted_access != ACCESS_READ)
++ sys_detect_dev_null_output ();
++
++ SET_BINARY_MODE (archive);
++}
++
+ /* Open an archive file. The argument specifies whether we are
+ reading or writing, or both. */
+ static void
+ _open_archive (enum access_mode wanted_access)
+ {
+- int backed_up_flag = 0;
++ bool backed_up_flag = false;
+
+ if (record_size == 0)
+ FATAL_ERROR ((0, 0, _("Invalid value for record_size")));
+@@ -796,15 +793,13 @@ _open_archive (enum access_mode wanted_a
+ {
+ case ACCESS_READ:
+ archive = open_compressed_archive ();
+- if (archive >= 0)
+- guess_seekable_archive ();
+ break;
+
+ case ACCESS_WRITE:
+ if (backup_option)
+ {
+ maybe_backup_file (archive_name_array[0], 1);
+- backed_up_flag = 1;
++ backed_up_flag = true;
+ }
+ if (verify_option)
+ archive = rmtopen (archive_name_array[0], O_RDWR | O_CREAT | O_BINARY,
+@@ -832,20 +827,7 @@ _open_archive (enum access_mode wanted_a
+ break;
+ }
+
+- if (archive < 0
+- || (! _isrmt (archive) && !sys_get_archive_stat ()))
+- {
+- int saved_errno = errno;
+-
+- if (backed_up_flag)
+- undo_last_backup ();
+- errno = saved_errno;
+- open_fatal (archive_name_array[0]);
+- }
+-
+- sys_detect_dev_null_output ();
+- sys_save_archive_dev_ino ();
+- SET_BINARY_MODE (archive);
++ get_archive_status (wanted_access, backed_up_flag);
+
+ switch (wanted_access)
+ {
+@@ -1048,18 +1030,8 @@ flush_archive (void)
+ static void
+ backspace_output (void)
+ {
+-#ifdef MTIOCTOP
+- {
+- struct mtop operation;
+-
+- operation.mt_op = MTBSR;
+- operation.mt_count = 1;
+- if (rmtioctl (archive, MTIOCTOP, (char *) &operation) >= 0)
+- return;
+- if (errno == EIO && rmtioctl (archive, MTIOCTOP, (char *) &operation) >= 0)
+- return;
+- }
+-#endif
++ if (mtioseek (false, -1))
++ return;
+
+ {
+ off_t position = rmtlseek (archive, (off_t) 0, SEEK_CUR);
+@@ -1372,7 +1344,6 @@ new_volume (enum access_mode mode)
+ case ACCESS_READ:
+ archive = rmtopen (*archive_name_cursor, O_RDONLY, MODE_RW,
+ rsh_command_option);
+- guess_seekable_archive ();
+ break;
+
+ case ACCESS_WRITE:
+@@ -1397,7 +1368,7 @@ new_volume (enum access_mode mode)
+ goto tryagain;
+ }
+
+- SET_BINARY_MODE (archive);
++ get_archive_status (mode, false);
+
+ return true;
+ }
+--- a/src/common.h
++++ b/src/common.h
+@@ -397,9 +397,8 @@ struct name
+ char *caname; /* canonical name */
+ };
+
+-/* Obnoxious test to see if dimwit is trying to dump the archive. */
+-GLOBAL dev_t ar_dev;
+-GLOBAL ino_t ar_ino;
++/* Status of archive file, or all zeros if remote. */
++GLOBAL struct stat archive_stat;
+
+ /* Flags for reading, searching, and fstatatting files. */
+ GLOBAL int open_read_flags;
+@@ -407,6 +406,9 @@ GLOBAL int open_searchdir_flags;
+ GLOBAL int fstatat_flags;
+
+ GLOBAL int seek_option;
++
++/* true if archive if lseek should be used on the archive, 0 if it
++ should not be used. */
+ GLOBAL bool seekable_archive;
+
+ GLOBAL dev_t root_device;
+@@ -894,7 +896,6 @@ void xheader_xattr_add (struct tar_stat_
+ /* Module system.c */
+
+ void sys_detect_dev_null_output (void);
+-void sys_save_archive_dev_ino (void);
+ void sys_wait_for_child (pid_t, bool);
+ void sys_spawn_shell (void);
+ bool sys_compare_uid (struct stat *a, struct stat *b);
+@@ -912,6 +913,7 @@ int sys_exec_info_script (const char **a
+ void sys_exec_checkpoint_script (const char *script_name,
+ const char *archive_name,
+ int checkpoint_number);
++bool mtioseek (bool count_files, off_t count);
+
+ /* Module compare.c */
+ void report_difference (struct tar_stat_info *st, const char *message, ...)
+--- a/src/compare.c
++++ b/src/compare.c
+@@ -566,31 +566,12 @@ verify_volume (void)
+ ioctl (archive, FDFLUSH);
+ #endif
+
+-#ifdef MTIOCTOP
+- {
+- struct mtop operation;
+- int status;
+-
+- operation.mt_op = MTBSF;
+- operation.mt_count = 1;
+- if (status = rmtioctl (archive, MTIOCTOP, (char *) &operation), status < 0)
+- {
+- if (errno != EIO
+- || (status = rmtioctl (archive, MTIOCTOP, (char *) &operation),
+- status < 0))
+- {
+-#endif
+- if (rmtlseek (archive, (off_t) 0, SEEK_SET) != 0)
+- {
+- /* Lseek failed. Try a different method. */
+- seek_warn (archive_name_array[0]);
+- return;
+- }
+-#ifdef MTIOCTOP
+- }
+- }
+- }
+-#endif
++ if (!mtioseek (true, -1) && rmtlseek (archive, 0, SEEK_SET) != 0)
++ {
++ /* Lseek failed. Try a different method. */
++ seek_warn (archive_name_array[0]);
++ return;
++ }
+
+ access_mode = ACCESS_READ;
+ now_verifying = 1;
+--- a/src/delete.c
++++ b/src/delete.c
+@@ -18,7 +18,6 @@
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+ #include <system.h>
+-#include <system-ioctl.h>
+
+ #include "common.h"
+ #include <rmt.h>
+@@ -50,41 +49,25 @@ move_archive (off_t count)
+ if (count == 0)
+ return;
+
+-#ifdef MTIOCTOP
+- {
+- struct mtop operation;
+-
+- if (count < 0
+- ? (operation.mt_op = MTBSR,
+- operation.mt_count = -count,
+- operation.mt_count == -count)
+- : (operation.mt_op = MTFSR,
+- operation.mt_count = count,
+- operation.mt_count == count))
+- {
+- if (0 <= rmtioctl (archive, MTIOCTOP, (char *) &operation))
+- return;
++ if (mtioseek (false, count))
++ return;
+
+- if (errno == EIO
+- && 0 <= rmtioctl (archive, MTIOCTOP, (char *) &operation))
++ off_t position0 = rmtlseek (archive, 0, SEEK_CUR), position = 0;
++ if (0 <= position0)
++ {
++ off_t increment;
++ if (INT_MULTIPLY_WRAPV (record_size, count, &increment)
++ || INT_ADD_WRAPV (position0, increment, &position)
++ || position < 0)
++ {
++ ERROR ((0, EOVERFLOW, "lseek: %s", archive_name_array[0]));
+ return;
+- }
+- }
+-#endif /* MTIOCTOP */
+-
+- {
+- off_t position0 = rmtlseek (archive, (off_t) 0, SEEK_CUR);
+- off_t increment = record_size * (off_t) count;
+- off_t position = position0 + increment;
+-
+- if (increment / count != record_size
+- || (position < position0) != (increment < 0)
+- || (position = position < 0 ? 0 : position,
+- rmtlseek (archive, position, SEEK_SET) != position))
+- seek_error_details (archive_name_array[0], position);
+-
+- return;
+- }
++ }
++ else if (rmtlseek (archive, position, SEEK_SET) == position)
++ return;
++ }
++ if (!_isrmt (archive))
++ seek_error_details (archive_name_array[0], position);
+ }
+
+ /* Write out the record which has been filled. If MOVE_BACK_FLAG,
+--- a/src/system.c
++++ b/src/system.c
+@@ -16,6 +16,7 @@
+ with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+ #include <system.h>
++#include <system-ioctl.h>
+
+ #include "common.h"
+ #include <priv-set.h>
+@@ -37,6 +38,35 @@ xexec (const char *cmd)
+ exec_fatal (cmd);
+ }
+
++/* True if the archive is seekable via ioctl and MTIOCTOP,
++ or if it is not known whether it is seekable.
++ False if it is known to be not seekable. */
++static bool mtioseekable_archive;
++
++bool
++mtioseek (bool count_files, off_t count)
++{
++ if (mtioseekable_archive)
++ {
++#ifdef MTIOCTOP
++ struct mtop operation;
++ operation.mt_op = (count_files
++ ? (count < 0 ? MTBSF : MTFSF)
++ : (count < 0 ? MTBSR : MTFSR));
++ if (! (count < 0
++ ? INT_SUBTRACT_WRAPV (0, count, &operation.mt_count)
++ : INT_ADD_WRAPV (count, 0, &operation.mt_count))
++ && (0 <= rmtioctl (archive, MTIOCTOP, &operation)
++ || (errno == EIO
++ && 0 <= rmtioctl (archive, MTIOCTOP, &operation))))
++ return true;
++#endif
++
++ mtioseekable_archive = false;
++ }
++ return false;
++}
++
+ #if MSDOS
+
+ bool
+@@ -52,11 +82,6 @@ sys_file_is_archive (struct tar_stat_inf
+ }
+
+ void
+-sys_save_archive_dev_ino (void)
+-{
+-}
+-
+-void
+ sys_detect_dev_null_output (void)
+ {
+ static char const dev_null[] = "nul";
+@@ -128,31 +153,34 @@ sys_child_open_for_uncompress (void)
+
+ extern union block *record_start; /* FIXME */
+
+-static struct stat archive_stat; /* stat block for archive file */
+-
+ bool
+ sys_get_archive_stat (void)
+ {
+- return fstat (archive, &archive_stat) == 0;
++ bool remote = _isrmt (archive);
++ mtioseekable_archive = true;
++ if (!remote && 0 <= archive && fstat (archive, &archive_stat) == 0)
++ {
++ if (!S_ISCHR (archive_stat.st_mode))
++ mtioseekable_archive = false;
++ return true;
++ }
++ else
++ {
++ /* FIXME: This memset should not be needed. It is present only
++ because other parts of tar may incorrectly access
++ archive_stat even if it's not the archive status. */
++ memset (&archive_stat, 0, sizeof archive_stat);
++
++ return remote;
++ }
+ }
+
+ bool
+ sys_file_is_archive (struct tar_stat_info *p)
+ {
+- return (ar_dev && p->stat.st_dev == ar_dev && p->stat.st_ino == ar_ino);
+-}
+-
+-/* Save archive file inode and device numbers */
+-void
+-sys_save_archive_dev_ino (void)
+-{
+- if (!_isrmt (archive) && S_ISREG (archive_stat.st_mode))
+- {
+- ar_dev = archive_stat.st_dev;
+- ar_ino = archive_stat.st_ino;
+- }
+- else
+- ar_dev = 0;
++ return (!dev_null_output && !_isrmt (archive)
++ && p->stat.st_dev == archive_stat.st_dev
++ && p->stat.st_ino == archive_stat.st_ino);
+ }
+
+ /* Detect if outputting to "/dev/null". */
+@@ -160,14 +188,15 @@ void
+ sys_detect_dev_null_output (void)
+ {
+ static char const dev_null[] = "/dev/null";
+- struct stat dev_null_stat;
++ static struct stat dev_null_stat;
+
+ dev_null_output = (strcmp (archive_name_array[0], dev_null) == 0
+ || (! _isrmt (archive)
+ && S_ISCHR (archive_stat.st_mode)
+- && stat (dev_null, &dev_null_stat) == 0
+- && archive_stat.st_dev == dev_null_stat.st_dev
+- && archive_stat.st_ino == dev_null_stat.st_ino));
++ && (dev_null_stat.st_ino != 0
++ || stat (dev_null, &dev_null_stat) == 0)
++ && archive_stat.st_ino == dev_null_stat.st_ino
++ && archive_stat.st_dev == dev_null_stat.st_dev));
+ }
+
+ void
projects / openwrt / staging / thess.git / commitdiff