File descriptor error for pdflatex.fmt creation on android 11

[Henrik Grimler]

Hello again, 

I have created a small test program (attached as test.c) that
reproduces the problem by condensing the relevant code in
texk/web2c/texmfmp.h and texk/web2c/lib/openclose.c.

It compiles without errors with clang-11 on both android (arm) and
linux (x86_64) with `clang -lz -o test test_reproduced.c`, and works
fine on linux, but when run on android it gives one of those file
descriptor errors:

fdsan: attempted to close file descriptor 3, expected to be unowned,
actually owned by FILE* 0xacdb000c

The problem seem to have to do with how the format file is opened. In
texmfmp.h we have:

```c
#define wopenout(f) (open_output ((FILE**)&(f), FOPEN_WBIN_MODE) \
 && (f = gzdopen(fileno((FILE*)f), FOPEN_WBIN_MODE)) \
 && (gzsetparams(f, 1, Z_DEFAULT_STRATEGY) == Z_OK))
```

If I convert the macro into a function instead:

```c
int wopenout (gzFile f)
{
  open_output ((FILE**)&(f), "wb");
  f = gzdopen(fileno((FILE*)f), "wb");
  return gzsetparams(f, 1, Z_DEFAULT_STRATEGY) == Z_OK;
}
```

the error no longer occurs. 

My first thought was that the issue is related to how gzFile is casted
to FILE, but since the problem disappears when defined as a function I
suppose this might be a bug in the android libc and/or fd sanitizer. 

Could macros, as the one defined for wopenout, be problematic? I.e.
would it make sense to convert wopenout into a normal function or is
this most likely an android-specific bug?

Best regards,
Henrik Grimler



On Fri, 2021-04-02 at 15:45 +0200, Henrik Grimler wrote:
> Dear all,
> 
> Android 11 introduced a new file descriptor sanitizer ("fdsan", see [1]
> for docs) which detects possible issues when opening and closing files
> across multiple threads.
> 
> Installing texlive on android 11 gives a fdsan error when creating
> pdflatex.fmt. If I run:
> 
>   pdftex -ini -jobname=pdflatex -progname=pdflatex -translate-
> file=cp227.tcx *pdflatex.ini
> 
> it aborts with an error
> 
>   fdsan: attempted to close file descriptor 3, expected to be unowned,
> actually owned by FILE* 0xb6c6100c
> 
> Does anyone have experience with this type of issue? For debugging it
> the docs suggests replacing all `int fd` with a special `unique_fd fd`
> type, but I am not yet sure how to use that for software like texlive
> (rather than android apps), so any hints are greatly appreciated.
> 
> If I run the command above in gdb I get this backtrace (see [2] for
> full log):
> 
> [...]
> Hyphenation trie of length 6081 has 183 ops out of 35111
>   2 for language 1
>   181 for language 0
> 0 words of pdfTeX memory
> fdsan: attempted to close file descriptor 3, expected to be unowned,
> actually owned by FILE* 0xb6c6100c
> 
> Program received signal SIGABRT, Aborted.
> 0xb64ec9e8 in fdsan_error(char const*, ...) () from
> /apex/com.android.runtime/lib/bionic/libc.so
> (gdb) bt
> #0  0xb64ec9e8 in fdsan_error(char const*, ...) () from
> /apex/com.android.runtime/lib/bionic/libc.so
> #1  0xb64ec6fe in android_fdsan_close_with_tag () from
> /apex/com.android.runtime/lib/bionic/libc.so
> #2  0xb64ecd6e in close () from
> /apex/com.android.runtime/lib/bionic/libc.so
> #3  0xb68b18f4 in gzclose_w () from
> /data/data/com.termux/files/usr/lib/libz.so.1.2.11
> #4  0x7f56abd8 in storefmtfile () at pdftexini.c:3584
> #5  0x7f570806 in mainbody () at pdftexini.c:5651
> #6  0x7f5609c0 in main (ac=<optimized out>, av=<optimized out>)
>     at /home/builder/.termux-build/texlive-
> bin/src/texk/web2c/lib/texmfmp.c:1098
> 
> The above output is for pdftex built from the svn54456 tag. 
> Please let me know if I can provide any additional information!
> 
> Best regards
> Henrik Grimler
> 
> [1]
> https://android.googlesource.com/platform/bionic/+/master/docs/fdsan.md
> [2] https://grimler.se/logs/pdftex.log
> 

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