On Sat, 3 Jun 2023, Demi Marie Obenour wrote:
> The NUL terminator for each target parameter string must precede the
> following 'struct dm_target_spec'. Otherwise, dm_split_args() might
> corrupt this struct. Furthermore, the first 'struct dm_target_spec'
> must come after the 'struct dm_ioctl', as if it overlaps too much
> dm_split_args() could corrupt the 'struct dm_ioctl'.
>
> Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> ---
> drivers/md/dm-ioctl.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 64e8f16d344c47057de5e2d29e3d63202197dca0..da6ca26b51d0953df380582bb3a51c2ec22c27cb 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1391,7 +1391,7 @@ static inline fmode_t get_mode(struct dm_ioctl *param)
> return mode;
> }
>
> -static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
> +static int next_target(struct dm_target_spec *last, uint32_t next, const char *end,
> struct dm_target_spec **spec, char **target_params)
> {
> static_assert(_Alignof(struct dm_target_spec) <= 8,
> @@ -1404,7 +1404,7 @@ static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
> * sizeof(struct dm_target_spec) or more, as otherwise *last was
> * out of bounds already.
> */
> - size_t remaining = (char *)end - (char *)last;
> + size_t remaining = end - (char *)last;
>
> /*
> * There must be room for both the next target spec and the
> @@ -1423,10 +1423,7 @@ static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
> *spec = (struct dm_target_spec *) ((unsigned char *) last + next);
> *target_params = (char *) (*spec + 1);
>
> - if (*spec < (last + 1))
> - return -EINVAL;
> -
> - return invalid_str(*target_params, end);
> + return 0;
> }
>
> static int populate_table(struct dm_table *table,
> @@ -1436,8 +1433,9 @@ static int populate_table(struct dm_table *table,
> unsigned int i = 0;
> struct dm_target_spec *spec = (struct dm_target_spec *) param;
> uint32_t next = param->data_start;
> - void *end = (void *) param + param_size;
> + const char *const end = (const char *) param + param_size;
> char *target_params;
> + size_t min_size = sizeof(struct dm_ioctl);
>
> if (!param->target_count) {
> DMERR("%s: no targets specified", __func__);
> @@ -1445,6 +1443,13 @@ static int populate_table(struct dm_table *table,
> }
>
> for (i = 0; i < param->target_count; i++) {
> + const char *nul_terminator;
> +
> + if (next < min_size) {
> + DMERR("%s: next target spec (offset %u) overlaps %s",
> + __func__, next, i ? "previous target" : "'struct dm_ioctl'");
> + return -EINVAL;
> + }
>
> r = next_target(spec, next, end, &spec, &target_params);
> if (r) {
> @@ -1452,6 +1457,15 @@ static int populate_table(struct dm_table *table,
> return r;
> }
>
> + nul_terminator = memchr(target_params, 0, (size_t)(end - target_params));
> + if (nul_terminator == NULL) {
> + DMERR("%s: target parameters not NUL-terminated", __func__);
> + return -EINVAL;
> + }
> +
> + /* Add 1 for NUL terminator */
> + min_size = (size_t)(nul_terminator - (const char *)spec) + 1;
> +
> r = dm_table_add_target(table, spec->target_type,
> (sector_t) spec->sector_start,
> (sector_t) spec->length,
> --
> Sincerely,
> Demi Marie Obenour (she/her/hers)
> Invisible Things Lab
>
> --
> dm-devel mailing list
> dm-devel@xxxxxxxxxx
> https://listman.redhat.com/mailman/listinfo/dm-devel
>
