Re: [PATCH v3 06/11] mm/util: Deduplicate code in {kstrdup,kstrndup,kmemdup_nul}
From: Simon Horman <horms@kernel.org>
Date: 2024-06-21 13:51:47
Also in:
bpf, dri-devel, linux-fsdevel, linux-mm, linux-security-module, netdev, selinux
On Fri, Jun 21, 2024 at 10:29:54AM +0800, Yafang Shao wrote:
These three functions follow the same pattern. To deduplicate the code, let's introduce a common help __kstrndup(). Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Yafang Shao <redacted>
Hi Yafang Shao, Some minor nits from my side.
quoted hunk ↗ jump to hunk
--- mm/internal.h | 24 ++++++++++++++++++++++++ mm/util.c | 27 ++++----------------------- 2 files changed, 28 insertions(+), 23 deletions(-)diff --git a/mm/internal.h b/mm/internal.h index b2c75b12014e..fd87f685739b 100644 --- a/mm/internal.h +++ b/mm/internal.h@@ -1521,4 +1521,28 @@ static inline void shrinker_debugfs_remove(struct dentry *debugfs_entry, void workingset_update_node(struct xa_node *node); extern struct list_lru shadow_nodes; +/** + * __kstrndup - Create a NUL-terminated string from @s, which might be unterminated. + * @s: The data to stringify + * @len: The size of the data, including the null terminator + * @gfp: the GFP mask used in the kmalloc() call when allocating memory + * + * Return: newly allocated copy of @s with NUL-termination or %NULL in + * case of error + */ +static __always_inline char *__kstrndup(const char *s, size_t len, gfp_t gfp) +{ + char *buf; + + buf = kmalloc_track_caller(len, gfp); + if (!buf) + return NULL; + + memcpy(buf, s, len); + /* Ensure the buf is always NUL-terminated, regardless of @s. */ + buf[len - 1] = '\0'; + return buf; +} + +
nit: One blank line is enough.
quoted hunk ↗ jump to hunk
#endif /* __MM_INTERNAL_H */diff --git a/mm/util.c b/mm/util.c index 41c7875572ed..d9135c5fdf7f 100644 --- a/mm/util.c +++ b/mm/util.c@@ -58,17 +58,8 @@ char *kstrdup(const char *s, gfp_t gfp) if (!s) return NULL; - len = strlen(s) + 1; - buf = kmalloc_track_caller(len, gfp); - if (buf) { - memcpy(buf, s, len); - /* During memcpy(), the string might be updated to a new value, - * which could be longer than the string when strlen() is - * called. Therefore, we need to add a null termimator. - */ - buf[len - 1] = '\0'; - } - return buf;
nit: The local variable buf is now unused, and should be removed from kstrdup().
Likewise for kstrndup() and kmemdup_nul()
Flagged by W=1 builds with gcc-13 and clang-18, and Smatch.
quoted hunk ↗ jump to hunk
+ len = strlen(s); + return __kstrndup(s, len + 1, gfp); } EXPORT_SYMBOL(kstrdup);@@ -111,12 +102,7 @@ char *kstrndup(const char *s, size_t max, gfp_t gfp) return NULL; len = strnlen(s, max); - buf = kmalloc_track_caller(len+1, gfp); - if (buf) { - memcpy(buf, s, len); - buf[len] = '\0'; - } - return buf; + return __kstrndup(s, len + 1, gfp); } EXPORT_SYMBOL(kstrndup);@@ -195,12 +181,7 @@ char *kmemdup_nul(const char *s, size_t len, gfp_t gfp) if (!s) return NULL; - buf = kmalloc_track_caller(len + 1, gfp); - if (buf) { - memcpy(buf, s, len); - buf[len] = '\0'; - } - return buf; + return __kstrndup(s, len + 1, gfp); } EXPORT_SYMBOL(kmemdup_nul);-- 2.39.1