Hi,

On Mon, Aug 01, 2022 at 02:09:52AM +0200, Mark Wielaard wrote:
> > - 7: make check ( failure )
> >     Logs:
> >         - stdio: https://builder.sourceware.org/buildbot/#builders/43/builds/47/steps/7/logs/stdio
> >         - test-suite.log: https://builder.sourceware.org/buildbot/#builders/43/builds/47/steps/7/logs/test-suite_log
> 
> So that is in the one little addition I made:
> 
> -==3856043== Invalid read of size 1
> -==3856043==    at 0x484EBE8: memrchr (vg_replace_strmem.c:1012)
> -==3856043==    by 0x100FEDF: handle_dynamic (readelf.c:1909)
> -==3856043==    by 0x102061D: print_dynamic (readelf.c:2013)
> -==3856043==    by 0x102061D: process_elf_file (readelf.c:1034)
> -==3856043==    by 0x1021FDB: process_dwflmod (readelf.c:818)
> -==3856043==    by 0x4962BCF: dwfl_getmodules (dwfl_getmodules.c:86)
> -==3856043==    by 0x100E175: process_file (readelf.c:926)
> -==3856043==    by 0x1006A75: main (readelf.c:395)
> -==3856043==  Address 0x56df358 is 24 bytes before a block of size 264 alloc'd
> -==3856043==    at 0x484C002: calloc (vg_replace_malloc.c:1328)
> -==3856043==    by 0x4A4EED9: elf_getdata_rawchunk (elf_getdata_rawchunk.c:173)
> -==3856043==    by 0x1010621: get_dynscn_strtab (readelf.c:4958)
> -==3856043==    by 0x1010621: handle_dynamic (readelf.c:1884)
> -==3856043==    by 0x102061D: print_dynamic (readelf.c:2013)
> -==3856043==    by 0x102061D: process_elf_file (readelf.c:1034)
> -==3856043==    by 0x1021FDB: process_dwflmod (readelf.c:818)
> -==3856043==    by 0x4962BCF: dwfl_getmodules (dwfl_getmodules.c:86)
> -==3856043==    by 0x100E175: process_file (readelf.c:926)
> -==3856043==    by 0x1006A75: main (readelf.c:395)
> 
> I am staring at the code, but don't immediately see which mistake I
> made.  Maybe I should use d_val instead of d_ptr (but those are both
> uint64_t so that shouldn't really matter).

Doh. Even though memchr searches backwards, it takes the start of the
buffer instead of the end of the buffer as argument. Fixed as
attached, also cleaned up the use of d_val vs d_ptr. Pushed after
verifying with a try- build that it really fixes the issue.

Cheers,

Mark