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authorTejun Heo <tj@kernel.org>2018-01-09 07:21:15 -0800
committerTejun Heo <tj@kernel.org>2018-01-19 08:51:36 -0800
commit08a77676f9c5fc69a681ccd2cd8140e65dcb26c7 (patch)
parent2c4736d9898a16b67bb31c03de166b3abaa5311a (diff)
string: drop __must_check from strscpy() and restore strscpy() usages in cgroup
e7fd37ba1217 ("cgroup: avoid copying strings longer than the buffers") converted possibly unsafe strncpy() usages in cgroup to strscpy(). However, although the callsites are completely fine with truncated copied, because strscpy() is marked __must_check, it led to the following warnings. kernel/cgroup/cgroup.c: In function ‘cgroup_file_name’: kernel/cgroup/cgroup.c:1400:10: warning: ignoring return value of ‘strscpy’, declared with attribute warn_unused_result [-Wunused-result] strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX); ^ To avoid the warnings, 50034ed49645 ("cgroup: use strlcpy() instead of strscpy() to avoid spurious warning") switched them to strlcpy(). strlcpy() is worse than strlcpy() because it unconditionally runs strlen() on the source string, and the only reason we switched to strlcpy() here was because it was lacking __must_check, which doesn't reflect any material differences between the two function. It's just that someone added __must_check to strscpy() and not to strlcpy(). These basic string copy operations are used in variety of ways, and one of not-so-uncommon use cases is safely handling truncated copies, where the caller naturally doesn't care about the return value. The __must_check doesn't match the actual use cases and forces users to opt for inferior variants which lack __must_check by happenstance or spread ugly (void) casts. Remove __must_check from strscpy() and restore strscpy() usages in cgroup. Signed-off-by: Tejun Heo <tj@kernel.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ma Shimiao <mashimiao.fnst@cn.fujitsu.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Chris Metcalf <cmetcalf@ezchip.com>
2 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/string.h b/include/linux/string.h
index 410ecf17de3c..dfdf8afeac64 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -28,7 +28,7 @@ extern char * strncpy(char *,const char *, __kernel_size_t);
size_t strlcpy(char *, const char *, size_t);
-ssize_t __must_check strscpy(char *, const char *, size_t);
+ssize_t strscpy(char *, const char *, size_t);
extern char * strcat(char *, const char *);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 7e4c44538119..8cda3bc3ae22 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1397,7 +1397,7 @@ static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
- strlcpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
+ strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
return buf;
@@ -1864,9 +1864,9 @@ void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts)
root->flags = opts->flags;
if (opts->release_agent)
- strlcpy(root->release_agent_path, opts->release_agent, PATH_MAX);
+ strscpy(root->release_agent_path, opts->release_agent, PATH_MAX);
if (opts->name)
- strlcpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
+ strscpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
if (opts->cpuset_clone_children)
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);