Package: pxz
Version: 4.999.99~beta5+gitfcfea93-1
Severity: important
Dear Maintainer,
pxz seems to ignore errors when writing to the temporary output
files used by the parallel compression threads, and silently
creates a corrupted output file.
to reproduce the bug (by using an extremely small /tmp dir, and
the bash builtin random number generator as a data source):
# mkdir -p /tmp
# mount -t tmpfs tmpfs /tmp/ -o size=512k
# RANDOM=0; while [[ true ]]; do echo $RANDOM; done | dd bs=1M
iflag=fullblock count=4 | ltrace -s0 -f -o trace pxz -T16 -f > out.bin.xz
observe the corrupted output file:
xz -l out.bin.xz
xz: out.bin.xz: File format not recognized
also observe the failed writes (where the number of bytes to
write out is not equal to the number of bytes actually written):
# awk '/fwrite/{ if(int($4) != int($7)){ print $0; } }' < trace
32159 fwrite(""..., 1, 61444, 0x1c380e0)
= 32705
32159 fwrite(""..., 1, 61444, 0x1c380e0)
= 4096
32159 fwrite(""..., 1, 61444, 0x1c380e0)
= 4096
32159 fwrite(""..., 1, 61444, 0x1c380e0)
= 4096
...
if you use strace instead of ltrace, you can see the actual ENOSPC error:
# RANDOM=0; while [[ true ]]; do echo $RANDOM; done | dd bs=1M
iflag=fullblock count=4 | strace -s0 -f -o trace pxz -T16 -f > out.bin.xz
# grep 'write.* = -1' trace
32241 write(3, ""..., 28672) = -1 ENOSPC (No space left on
device)
32241 write(3, ""..., 4096) = -1 ENOSPC (No space left on
device)
32241 write(3, ""..., 4096) = -1 ENOSPC (No space left on
device)
32241 write(3, ""..., 4096) = -1 ENOSPC (No space left on
device)
...
looking at pxz's source in the git repository, the error
checking after some fwrite() calls is erroneous:
https://github.com/jnovy/pxz/blob/fcfea93/pxz.c#L391
https://github.com/jnovy/pxz/blob/fcfea93/pxz.c#L408
if ( !fwrite(mo, 1, BUFFSIZE - strm.avail_out, ftemp[p]) ) {
error(EXIT_FAILURE, errno, "writing to temp file failed");
}
it should be at least
if ( fwrite(mo, 1, BUFFSIZE - strm.avail_out, ftemp[p]) != BUFFSIZE -
strm.avail_out ) {
just like at other parts of the program.
-- System Information:
Debian Release: 8.0
APT prefers stable
APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)
Versions of packages pxz depends on:
ii libc6 2.19-18+deb8u1
ii libgomp1 4.9.2-10
ii liblzma5 5.1.1alpha+20120614-2+b3
pxz recommends no packages.
pxz suggests no packages.
-- no debconf information
--
mazsi
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strawberry fields forever! mazsi-debian-b...@imrek.org
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