#152 Zip: Archiving hangs, if there is no read permission on the file

[Mizuno]

If you simply create two files and pack them, it's all right

$ touch 1
$ touch 2
$ 7za a 1.zip 1 2

7-Zip (a) [64] 9.38 beta Copyright (c) 1999-2014 Igor Pavlov 2015-01-03
p7zip Version 9.38.1 (locale=ru_RU.UTF-8,Utf16=on,HugeFiles=on,8 CPUs,ASM)
Scanning

Creating archive 1.zip

Compressing 1
Compressing 2

Everything is Ok

But if one file can not be read, then packing hangs

$ chmod 0000 2
$ 7za a 2.zip 1 2

7-Zip (a) [64] 9.38 beta Copyright (c) 1999-2014 Igor Pavlov 2015-01-03
p7zip Version 9.38.1 (locale=ru_RU.UTF-8,Utf16=on,HugeFiles=on,8 CPUs,ASM)
Scanning

Creating archive 2.zip

Compressing 1
Compressing 2

<hang></hang>

Tested in ubuntu and Centos 5
The problem occurs only when run as an unprivileged user. As root - all right

[md-work]

Still a problem in p7zip-16.02.

Proposal:
The "WARNING: Permission denied" is good.
But afterwards 7z should continue the compression for the readable files.
And finally 7z should exit with an exit code != 0.

Tested on openSUSE-15.2:

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=C,Utf16=off,HugeFiles=on,64 bits,2 CPUs QEMU Virtual CPU version 2.5+ (663),ASM)

Open archive: ../rw/test.zip
--
Path = ../rw/test.zip
Type = zip
Physical Size = 22

Scanning the drive:
2 files, 0 bytes

Updating archive: ../rw/test.zip

Items to compress: 2


WARNING: Permission denied
2

[Sam Tansy]

Only with zip files though. When using 7z it's fine, program ignores inaccessible file and moves on.

$ echo -n "1" > 1; echo -n "22" > 22
$ chmod 0000 22
$ rm *.7z; ./7za a 12b.7z 1 22


Scanning the drive:
2 files, 3 bytes (1 KiB)

Creating archive: 12b.7z

Items to compress: 2


WARNING: Permission denied
22


Files read from disk: 2
Archive size: 134 bytes (1 KiB)

WARNINGS for files:

22 : Permission denied
----------------
WARNING: Cannot open 1 file

Back to the problem, I tried to use gdb and strace and all I found put is this:
in gdb program hangs in libpthreads.so:

$(gdb)
Program received signal SIGINT, Interrupt.
0xb7fbbfed in ?? () from /lib/libpthread.so.0
(gdb) bt
#0  0xb7fbbfed in ?? () from /lib/libpthread.so.0
#1  0xb7fb7bf9 in ?? () from /lib/libpthread.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) where
#0  0xb7fbbfed in ?? () from /lib/libpthread.so.0
#1  0xb7fb7bf9 in ?? () from /lib/libpthread.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

and strace somewhere here:

clone(child_stack=0xb288f424, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0xb288fba8, {entry_number:6, base_addr:0xb288fb40, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}, child_tidptr=0xb288fba8) = 12714
gettimeofday({1616099717, 264583}, NULL) = 0
umask(0)                                = 022
umask(022)                              = 0
readlink("1", 0x8682358, 1024)          = -1 EINVAL (Invalid argument)
open("1", O_RDONLY|O_LARGEFILE)         = 4
gettimeofday({1616099717, 264872}, NULL) = 0
umask(0)                                = 022
umask(022)                              = 0
readlink("22", 0x8682838, 1024)         = -1 EINVAL (Invalid argument)
open("22", O_RDONLY|O_LARGEFILE)        = -1 EACCES (Permission denied)
write(1, "\10\10\10\10    \10\10\10\10") = 12
write(2, "\n", 1
)                       = 1
write(2, "WARNING: ", 9WARNING: )                = 9
write(2, "Permission denied", 17Permission denied)       = 17
write(2, "\n", 1
)                       = 1
write(2, "22", 222)                       = 2
write(2, "\n", 1
)                       = 1
write(2, "\n", 1
)                       = 1
futex(0x8681dcc, FUTEX_WAIT_PRIVATE, 2, NULL
^C <unfinished ...>

which again made me think it has something to do with threads, so I made an experiment:

$ echo -n "1" > 1; echo -n "22" > 22
$ chmod 0000 22
$ rm *.zip; ./7za a -mmt1 12b.zip 1 22

Scanning the drive:
2 files, 3 bytes (1 KiB)

Creating archive: 12b.zip

Items to compress: 2


WARNING: Permission denied
22


Files read from disk: 2
Archive size: 137 bytes (1 KiB)

WARNINGS for files:

22 : Permission denied
----------------
WARNING: Cannot open 1 file

$ ls -l *.zip 
-rw-r--r-- 1 user users 137 Mar 18 22:11 12b.zip

$ 7z l 12b.zip

Listing archive: 12b.zip

--
Path = 12b.zip
Type = zip
Physical Size = 137

   Date      Time    Attr         Size   Compressed  Name
------------------- ----- ------------ ------------  ------------------------
2021-03-18 19:17:03 .....            1            1  1
------------------- ----- ------------ ------------  ------------------------
2021-03-18 19:17:03                  1            1  1 files

And it looks like I was right. When one turns off multiple treads, it works fine.

It obviously doesn't solve the problem but gives the hint where to look for.