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dm ioctl: replace deprecated strncpy with strscpy_pad

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`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect `spec->target_type` to be NUL-terminated based on its use with
a format string after `dm_table_add_target()` is called
| 	r = dm_table_add_target(table, spec->target_type,
| 				(sector_t) spec->sector_start,
| 				(sector_t) spec->length,
| 				target_params);
... wherein `spec->target_type` is passed as parameter `type` and later
printed with DMERR:
|       DMERR("%s: %s: unknown target type", dm_device_name(t->md), type);

It appears that `spec` is not zero-allocated and thus NUL-padding may be
required in this ioctl context.

Considering the above, a suitable replacement is `strscpy_pad` due to
the fact that it guarantees NUL-termination whilst maintaining the
NUL-padding behavior that strncpy provides.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Justin Stitt 2023-09-25 06:54:51 +00:00 committed by Mike Snitzer
parent e9d7bd2c86
commit 0ffb645ea8
1 changed files with 2 additions and 2 deletions
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4
drivers/md/dm-ioctl.c
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@ -1295,8 +1295,8 @@ static void retrieve_status(struct dm_table *table,
spec->status = 0; spec->status = 0;
spec->sector_start = ti->begin; spec->sector_start = ti->begin;
spec->length = ti->len; spec->length = ti->len;
strncpy(spec->target_type, ti->type->name, strscpy_pad(spec->target_type, ti->type->name,
sizeof(spec->target_type) - 1); sizeof(spec->target_type));
outptr += sizeof(struct dm_target_spec); outptr += sizeof(struct dm_target_spec);
remaining = len - (outptr - outbuf); remaining = len - (outptr - outbuf);