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authorJustin Stitt <justinstitt@google.com>2023-09-25 06:13:12 +0000
committerMike Snitzer <snitzer@kernel.org>2023-10-23 13:02:05 -0400
commitac4149ba7efd6bc327c1e15e812091984f3a16b2 (patch)
treeabdae55ab7fb5a4dd29b56e75aedc6bf003f35d9 /drivers/md
parentf1445032173d4a49eb8b4a0808db499966897d9a (diff)
dm cache metadata: replace deprecated strncpy with strscpy
`strncpy` is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. It seems `cmd->policy_name` is intended to be NUL-terminated based on a now changed line of code from Commit (c6b4fcbad044e6ff "dm: add cache target"): | if (strcmp(cmd->policy_name, policy_name)) { // ... However, now a length-bounded strncmp is used: | if (strncmp(cmd->policy_name, policy_name, sizeof(cmd->policy_name))) ... which means NUL-terminated may not strictly be required. However, I believe the intent of the code is clear and we should maintain NUL-termination of policy_names. Moreover, __begin_transaction_flags() zero-allocates `cmd` before calling read_superblock_fields(): | cmd = kzalloc(sizeof(*cmd), GFP_KERNEL); Also, `disk_super->policy_name` is zero-initialized | memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name)); ... therefore any NUL-padding is redundant. Considering the above, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. 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 Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Justin Stitt <justinstitt@google.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-cache-metadata.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index acffed750e3e..5a18b80d3666 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -597,7 +597,7 @@ static void read_superblock_fields(struct dm_cache_metadata *cmd,
cmd->discard_nr_blocks = to_dblock(le64_to_cpu(disk_super->discard_nr_blocks));
cmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
cmd->cache_blocks = to_cblock(le32_to_cpu(disk_super->cache_blocks));
- strncpy(cmd->policy_name, disk_super->policy_name, sizeof(cmd->policy_name));
+ strscpy(cmd->policy_name, disk_super->policy_name, sizeof(cmd->policy_name));
cmd->policy_version[0] = le32_to_cpu(disk_super->policy_version[0]);
cmd->policy_version[1] = le32_to_cpu(disk_super->policy_version[1]);
cmd->policy_version[2] = le32_to_cpu(disk_super->policy_version[2]);
@@ -707,7 +707,7 @@ static int __commit_transaction(struct dm_cache_metadata *cmd,
disk_super->discard_block_size = cpu_to_le64(cmd->discard_block_size);
disk_super->discard_nr_blocks = cpu_to_le64(from_dblock(cmd->discard_nr_blocks));
disk_super->cache_blocks = cpu_to_le32(from_cblock(cmd->cache_blocks));
- strncpy(disk_super->policy_name, cmd->policy_name, sizeof(disk_super->policy_name));
+ strscpy(disk_super->policy_name, cmd->policy_name, sizeof(disk_super->policy_name));
disk_super->policy_version[0] = cpu_to_le32(cmd->policy_version[0]);
disk_super->policy_version[1] = cpu_to_le32(cmd->policy_version[1]);
disk_super->policy_version[2] = cpu_to_le32(cmd->policy_version[2]);
@@ -1726,7 +1726,7 @@ static int write_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *po
(strlen(policy_name) > sizeof(cmd->policy_name) - 1))
return -EINVAL;
- strncpy(cmd->policy_name, policy_name, sizeof(cmd->policy_name));
+ strscpy(cmd->policy_name, policy_name, sizeof(cmd->policy_name));
memcpy(cmd->policy_version, policy_version, sizeof(cmd->policy_version));
hint_size = dm_cache_policy_get_hint_size(policy);