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unicode: Properly reject invalid encoding version strings

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Casefolding filesystems can request a specific version of UTF-8 at
mount-time.  utf8_parse_version then assembles the "major.minor.rev"
string into an unsigned int.  There were two issues with the parser
logic: first, individual fields are read as signed int, allowing
negative numbers, second, an overflowed field will result in unexpected
results. Something like the below actually succeeds to mount using
utf8-12.1.0.

 mount -t tmpfs -o casefold=utf8-12.0.256 none /mnt
[   10.867859] tmpfs: Using encoding : utf8-12.1.0

Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
This commit is contained in:
Gabriel Krisman Bertazi
2026-07-31 15:54:45 -04:00
parent 080241946e
commit a511442085
1 changed files with 5 additions and 3 deletions
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8
fs/unicode/utf8-core.c
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@@ -204,17 +204,19 @@ int utf8_parse_version(char *version)
substring_t args[3];
unsigned int maj, min, rev;
static const struct match_token token[] = {
{1, "%d.%d.%d"},
{1, "%u.%u.%u"},
{0, NULL}
};
if (match_token(version, token, args) != 1)
return -EINVAL;
if (match_int(&args[0], &maj) || match_int(&args[1], &min) ||
match_int(&args[2], &rev))
if (match_uint(&args[0], &maj) || match_uint(&args[1], &min) ||
match_uint(&args[2], &rev))
return -EINVAL;
if (maj > U8_MAX || min > U8_MAX || rev > U8_MAX)
return -EINVAL;
return UNICODE_AGE(maj, min, rev);
}
EXPORT_SYMBOL(utf8_parse_version);