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zdb: Handle theoretical buffer overflow when printing float 

CodeQL pointed out that for extreme floating point values, `sprintf()`
will overwrite a 32 character buffer. It cited 1e304 as an example,
which causes `sprintf()` to print 308 characters.

In practice, the numbers should never exceed 100, so this should not
happen. To silence the warning and also handle unexpected situations, we
change the code to use `snprintf()`.

This was missed during my audit of our use of `sprintf()`, since I did
not think to consider extreme floating point representations. It also
really should not happen, so this change is purely defensive
programming.

This was found by CodeQL's cpp/overrunning-write-with-float check.

Reviewed-by: Damian Szuberski <szuberskidamian@gmail.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #14264
This commit is contained in:
Richard Yao 2022-12-04 15:41:24 -05:00 committed by Brian Behlendorf
parent d30db519af
commit f954ea26a6
1 changed files with 3 additions and 3 deletions
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6
cmd/zdb/zdb.c
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@ -3496,9 +3496,9 @@ dump_object(objset_t *os, uint64_t object, int verbosity,
zdb_nicenum(doi.doi_physical_blocks_512 << 9, asize, sizeof (asize));
zdb_nicenum(doi.doi_bonus_size, bonus_size, sizeof (bonus_size));
zdb_nicenum(doi.doi_dnodesize, dnsize, sizeof (dnsize));
(void) sprintf(fill, "%6.2f", 100.0 * doi.doi_fill_count *
doi.doi_data_block_size / (object == 0 ? DNODES_PER_BLOCK : 1) /
doi.doi_max_offset);
(void) snprintf(fill, sizeof (fill), "%6.2f", 100.0 *
doi.doi_fill_count * doi.doi_data_block_size / (object == 0 ?
DNODES_PER_BLOCK : 1) / doi.doi_max_offset);
aux[0] = '\0';