[Debian-science-sagemath] Bug#844789: iS: issue related to compressed manual.six

[Bill Allombert]

On Thu, Nov 24, 2016 at 04:55:28AM +0000, Jerome BENOIT wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
> 
> Hello Again,
> 
> On 24/11/16 02:52, Jerome BENOIT wrote:
> > 
> > 
> > On 23/11/16 09:59, Bill Allombert wrote:
> >> Can you generate a full strace dump ?
> > 
> > Yes. Unfortunately I have not yet succeeded to decipher them.
> > 
> > There is a `Broken pipe' somewhere.
> > The piping seems to be related to the uncompresion of a `manual.siz.gx'.
> 
> There are a myriad of processes: the messages around the `Broken pipe' are:
> 
> execve("/bin/gunzip", ["gunzip"], [/* 90 vars */]) = 0
> [...]
> rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
> rt_sigaction(SIGHUP, NULL, {SIG_IGN, [], 0}, 8) = 0
> rt_sigaction(SIGPIPE, NULL, {SIG_IGN, [], 0}, 8) = 0
> rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
> rt_sigaction(SIGXCPU, NULL, {SIG_DFL, [], 0}, 8) = 0
> rt_sigaction(SIGXFSZ, NULL, {SIG_IGN, [], 0}, 8) = 0
> rt_sigaction(SIGINT, {0x4035c0, [INT TERM XCPU], SA_RESTORER, 0x7eff302e1040}, NULL, 8) = 0
> rt_sigaction(SIGTERM, {0x4035c0, [INT TERM XCPU], SA_RESTORER, 0x7eff302e1040}, NULL, 8) = 0
> rt_sigaction(SIGXCPU, {0x4035c0, [INT TERM XCPU], SA_RESTORER, 0x7eff302e1040}, NULL, 8) = 0
> ioctl(0, TCGETS, 0x7ffef9ddf1c0)        = -1 ENOTTY (Inappropriate ioctl for device)
> fstat(0, {st_mode=S_IFREG|0644, st_size=171476, ...}) = 0
> read(0, "\37\213\10\0\0\0\0\0\2\3\244\\\331\222\324H\226}\317\257\220\345\274T\233\1\346\3732c\363\240"..., 32768) = 32768
> brk(NULL)                               = 0x669000
> brk(0x68a000)                           = 0x68a000
> write(1, "#SIXFORMAT  GapDocGAP\nHELPBOOKIN"..., 32768) = 32768
> write(1, ".4-1\", [ 20, 4, 1 ], 98, 246, \"l"..., 32768) = 32768
> write(1, " \"35.3-5\", [ 35, 3, 5 ], 310, 46"..., 32768) = 16384
> - --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=9643, si_uid=1000} ---
> write(1, "033[101X\", \"41.10-2\", \n      [ 4"..., 16384) = -1 EPIPE (Broken pipe)
> - --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=9643, si_uid=1000} ---
> write(2, "\ngzip: ", 7)                 = 7
> write(2, "stdout: Broken pipe\n", 20)   = 20
> rt_sigprocmask(SIG_BLOCK, [INT TERM XCPU], [], 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> lseek(0, 0, SEEK_CUR)                   = 32768
> close(0)                                = 0
> close(1)                                = 0
> close(2)                                = 0
> exit_group(1)                           = ?
> +++ exited with 1 +++
> 
> [[/bin/gunzip is in fact a shell script that wraps `gzip -d' ]]
> 
> It looks like that it happens what is described in the following link:
> 
> https://blog.nelhage.com/2010/02/a-very-subtle-bug/
> 
> that is to say, python/sage manipulates SIGPIPE in such a way that any gzip piping
> becomes hazardous.

Can you confirm that 'CloseStream(stream);' is the call that trigger the
SIGPIPE ?  In which case this can be worked around.

Cheers
-- 
Bill. <ballombe at debian.org>

Imagine a large red swirl here.