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Subject[PATCH v2] mm: new primitive kvmemdup()
Date
Similar to kmemdup(), but support large amount of bytes with kvmalloc()
and does *not* guarantee that the result will be physically contiguous.
Use only in cases where kvmalloc() is needed and free it with kvfree().
Also adapt policy_unpack.c in case someone bisect into this.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Hao Sun <sunhao.th@gmail.com>
---
This pattern has been used in several places and we're also going to
do this[1], seems reasonable to add this so that bpf and in future
others could make use of it.

v1 -> v2 adapt policy_unpack.c to fix compile error

[1] https://lore.kernel.org/bpf/7d274284-0fcc-061c-582e-3dfb629c6a44@iogearbox.net/T/#t
---
include/linux/string.h | 1 +
mm/util.c | 24 +++++++++++++++++++++++-
security/apparmor/policy_unpack.c | 11 +----------
3 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index db28802ab0a6..c062c581a98b 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -177,6 +177,7 @@ extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
extern const char *kstrdup_const(const char *s, gfp_t gfp);
extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
+extern void *kvmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);

extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
diff --git a/mm/util.c b/mm/util.c
index b56c92fb910f..cec9327b27b4 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -120,7 +120,8 @@ EXPORT_SYMBOL(kstrndup);
* @len: memory region length
* @gfp: GFP mask to use
*
- * Return: newly allocated copy of @src or %NULL in case of error
+ * Return: newly allocated copy of @src or %NULL in case of error,
+ * result is physically contiguous. Use kfree() to free.
*/
void *kmemdup(const void *src, size_t len, gfp_t gfp)
{
@@ -133,6 +134,27 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
}
EXPORT_SYMBOL(kmemdup);

+/**
+ * kvmemdup - duplicate region of memory
+ *
+ * @src: memory region to duplicate
+ * @len: memory region length
+ * @gfp: GFP mask to use
+ *
+ * Return: newly allocated copy of @src or %NULL in case of error,
+ * result may be not physically contiguous. Use kvfree() to free.
+ */
+void *kvmemdup(const void *src, size_t len, gfp_t gfp)
+{
+ void *p;
+
+ p = kvmalloc(len, gfp);
+ if (p)
+ memcpy(p, src, len);
+ return p;
+}
+EXPORT_SYMBOL(kvmemdup);
+
/**
* kmemdup_nul - Create a NUL-terminated string from unterminated data
* @s: The data to stringify
diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
index 66915653108c..5e9949832af6 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -161,15 +161,6 @@ VISIBLE_IF_KUNIT bool aa_inbounds(struct aa_ext *e, size_t size)
}
EXPORT_SYMBOL_IF_KUNIT(aa_inbounds);

-static void *kvmemdup(const void *src, size_t len)
-{
- void *p = kvmalloc(len, GFP_KERNEL);
-
- if (p)
- memcpy(p, src, len);
- return p;
-}
-
/**
* aa_unpack_u16_chunk - test and do bounds checking for a u16 size based chunk
* @e: serialized data read head (NOT NULL)
@@ -1027,7 +1018,7 @@ static struct aa_profile *unpack_profile(struct aa_ext *e, char **ns_name)

data->key = key;
data->size = aa_unpack_blob(e, &data->data, NULL);
- data->data = kvmemdup(data->data, data->size);
+ data->data = kvmemdup(data->data, data->size, GFP_KERNEL);
if (data->size && !data->data) {
kfree_sensitive(data->key);
kfree_sensitive(data);
base-commit: b6bb9676f2165d518b35ba3bea5f1fcfc0d969bf
--
2.39.0

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