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udf: replace deprecated strncpy/strcpy with strscpy

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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. Also replace an instance of strcpy() which is also
deprecated.

s_volume_ident is a NUL-terminated string which is evident from its
usage in udf_debug:
|	udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);

s_volume_ident should also be NUL-padded as it is copied out to
userspace:
|	if (copy_to_user((char __user *)arg,
|				UDF_SB(inode->i_sb)->s_volume_ident, 32))
|		return -EFAULT;

Considering the above, a suitable replacement is `strscpy_pad` [2] due
to the fact that it guarantees both NUL-termination and NUL-padding on
the destination buffer.

To simplify the code, let's use the new 2-argument version of
strscpy_pad() introduced in Commit e6584c3964 ("string: Allow
2-argument strscpy()"). Also zero-allocate @outstr so we can safely use
a non-@ret length argument. This is just in case udf_dstrCS0toChar()
doesn't include the NUL-byte in its return length, we won't truncate
@outstr or write garbage bytes either.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20240401-strncpy-fs-udf-super-c-v1-1-80cddab7a281@google.com>
This commit is contained in:
Justin Stitt 2024-04-01 20:01:51 +00:00 committed by Jan Kara
parent 8777446a3f
commit 94755a00a4
1 changed files with 3 additions and 3 deletions
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6
fs/udf/super.c
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@ -895,7 +895,7 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
int ret;
struct timestamp *ts;
outstr = kmalloc(128, GFP_KERNEL);
outstr = kzalloc(128, GFP_KERNEL);
if (!outstr)
return -ENOMEM;
@ -921,11 +921,11 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
ret = udf_dstrCS0toChar(sb, outstr, 31, pvoldesc->volIdent, 32);
if (ret < 0) {
strcpy(UDF_SB(sb)->s_volume_ident, "InvalidName");
strscpy_pad(UDF_SB(sb)->s_volume_ident, "InvalidName");
pr_warn("incorrect volume identification, setting to "
"'InvalidName'\n");
} else {
strncpy(UDF_SB(sb)->s_volume_ident, outstr, ret);
strscpy_pad(UDF_SB(sb)->s_volume_ident, outstr);
}
udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);