[PATCH v2 05/16] device-mapper: Target parameters must not overlap next target spec

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

The NUL terminator for each target parameter string must preceed the
following 'struct dm_target_spec'.  Otherwise, dm_split_args() might
corrupt this struct.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/md/dm-ioctl.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 
9f505abba3dc22bffc6acb335c0bf29fec288fd5..491ef55b9e8662c3b02a2162b8c93ee086c078a1
 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
@@ -1423,7 +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);
 
-       return invalid_str(*target_params, end);
+       return 0;
 }
 
 static int populate_table(struct dm_table *table,
@@ -1433,24 +1433,21 @@ 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__);
                return -EINVAL;
        }
 
-       if (next < sizeof(struct dm_ioctl)) {
-               DMERR("%s: first target spec (offset %u) overlaps 'struct 
dm_ioctl'",
-                     __func__, next);
-               return -EINVAL;
-       }
-
        for (i = 0; i < param->target_count; i++) {
-               if (next < sizeof(*spec)) {
-                       DMERR("%s: next target spec (offset %u) overlaps 
'struct dm_target_spec'",
-                             __func__, next);
+               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;
                }
 
@@ -1460,6 +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 = (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