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Fix valgrind warning about write of uninitialized bytes in ScaleOffse… #3390

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merged 1 commit into from
Aug 18, 2023
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Fix valgrind warning about write of uninitialized bytes in ScaleOffse… #3390

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8 changes: 7 additions & 1 deletion src/H5Zscaleoffset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1283,6 +1283,9 @@ H5Z__filter_scaleoffset(unsigned flags, size_t cd_nelmts, const unsigned cd_valu
}
/* output; compress */
else {
size_t used_bytes;
size_t unused_bytes;

assert(nbytes == d_nelmts * p.size);

/* before preprocess, convert to memory endianness order if needed */
Expand Down Expand Up @@ -1334,7 +1337,10 @@ H5Z__filter_scaleoffset(unsigned flags, size_t cd_nelmts, const unsigned cd_valu
/* (Looks like an error in the original determination of how many
* bytes would be needed for parameters. - QAK, 2010/08/19)
*/
memset(outbuf + 13, 0, (size_t)8);
used_bytes = 4 + 1 + sizeof(unsigned long long);
assert(used_bytes <= size_out);
unused_bytes = size_out - used_bytes;
memset(outbuf + 13, 0, unused_bytes);
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The comment on line 1316 above implies that there may be an extra byte in the buffer at times. This memset was assuming the buffer is only 21 bytes, but I encountered a valgrind warning where the buffer is 22 bytes and so the last byte in the buffer was uninitialized when written to the file:

==32533== Syscall param pwritev(vector[2]) points to uninitialised byte(s)
==32533==    at 0x52CA758: pwritev (in /lib64/libc-2.37.so)
==32533==    by 0x86E4E45: mca_fbtl_posix_pwritev_generic (fbtl_posix_pwritev.c:290)
==32533==    by 0x86E435A: mca_fbtl_posix_pwritev (fbtl_posix_pwritev.c:74)
==32533==    by 0x8156100: mca_common_ompio_file_write (common_ompio_file_write.c:154)
==32533==    by 0x81632CD: mca_fcoll_individual_file_write_all (fcoll_individual_file_write_all.c:39)
==32533==    by 0x8156B1B: mca_common_ompio_file_write_all (common_ompio_file_write.c:431)
==32533==    by 0x8156B90: mca_common_ompio_file_write_at_all (common_ompio_file_write.c:452)
==32533==    by 0x80EC55D: mca_io_ompio_file_write_at_all (io_ompio_file_write.c:174)
==32533==    by 0x507DB07: PMPI_File_write_at_all (pfile_write_at_all.c:75)
==32533==    by 0x4A5AC63: H5FD__mpio_write (H5FDmpio.c:1587)
==32533==    by 0x4A49832: H5FD_write (H5FDint.c:308)
==32533==    by 0x4A0F230: H5F__accum_write (H5Faccum.c:820)
==32533==  Address 0x8c7add5 is 21 bytes inside a block of size 22 alloc'd
==32533==    at 0x48427B4: malloc (vg_replace_malloc.c:393)
==32533==    by 0x4B3E57A: H5MM_malloc (H5MM.c:80)
==32533==    by 0x4D467FF: H5Z__filter_scaleoffset (H5Zscaleoffset.c:1316)
==32533==    by 0x4D3CEA1: H5Z_pipeline (H5Z.c:1423)
==32533==    by 0x4989AC6: H5D__chunk_allocate (H5Dchunk.c:4978)
==32533==    by 0x49A478E: H5D__init_storage (H5Dint.c:2443)
==32533==    by 0x49AA641: H5D__alloc_storage (H5Dint.c:2353)
==32533==    by 0x49B37E8: H5D__layout_oh_create (H5Dlayout.c:479)
==32533==    by 0x49A3540: H5D__update_oh_info (H5Dint.c:978)
==32533==    by 0x49A62D5: H5D__create (H5Dint.c:1299)
==32533==    by 0x49C6067: H5O__dset_create (H5Doh.c:272)
==32533==    by 0x4B8163C: H5O_obj_create (H5Oint.c:2347)


/* special case: minbits equal to full precision */
if (minbits == p.size * 8) {
Expand Down