• Mikulas Patocka's avatar
    dm: reject trailing characters in sccanf input · 31998ef1
    Mikulas Patocka authored
    Device mapper uses sscanf to convert arguments to numbers. The problem is that
    the way we use it ignores additional unmatched characters in the scanned string.
    For example, this `if (sscanf(string, "%d", &number) == 1)' will match a number,
    but also it will match number with some garbage appended, like "123abc".
    As a result, device mapper accepts garbage after some numbers. For example
    the command `dmsetup create vg1-new --table "0 16384 linear 254:1bla 34816bla"'
    will pass without an error.
    This patch fixes all sscanf uses in device mapper. It appends "%c" with
    a pointer to a dummy character variable to every sscanf statement.
    The construct `if (sscanf(string, "%d%c", &number, &dummy) == 1)' succeeds
    only if string is a null-terminated number (optionally preceded by some
    whitespace characters). If there is some character appended after the number,
    sscanf matches "%c", writes the character to the dummy variable and returns 2.
    We check the return value for 1 and consequently reject numbers with some
    garbage appended.
    Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
dm-service-time.c 8.25 KB