On 30/07/24 11:23, Thorsten Blum wrote:
Add the __counted_by compiler attribute to the flexible array member
inodes to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.
Remove the now obsolete comment on the count field.
Refactor ext4_expand_inode_array() by assigning count before copying any
data using memcpy(). Copy only the inodes array instead of the whole
struct because count has been set explicitly.
Use struct_size() and struct_size_t() instead of offsetof().
Change the data type of the local variable count to unsigned int to
match the struct's count data type.
Compile-tested only.
Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxxx>
---
Changes in v2:
- Adjust ext4_expand_inode_array() as suggested by Gustavo A. R. Silva
- Use struct_size() and struct_size_t() instead of offsetof()
- Link to v1: https://lore.kernel.org/linux-kernel/20240729110454.346918-3-thorsten.blum@xxxxxxxxxx/
---
fs/ext4/xattr.c | 20 +++++++++-----------
fs/ext4/xattr.h | 4 ++--
2 files changed, 11 insertions(+), 13 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 46ce2f21fef9..b27543587103 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2879,11 +2879,10 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
if (*ea_inode_array == NULL) {
/*
* Start with 15 inodes, so it fits into a power-of-two size.
- * If *ea_inode_array is NULL, this is essentially offsetof()
*/
(*ea_inode_array) =
- kmalloc(offsetof(struct ext4_xattr_inode_array,
- inodes[EIA_MASK]),
+ kmalloc(struct_size_t(struct ext4_xattr_inode_array,
+ inodes, EIA_MASK),
As Kees previously commented, you can use struct_size() here.
GFP_NOFS);
if (*ea_inode_array == NULL)
return -ENOMEM;
@@ -2891,17 +2890,16 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
} else if (((*ea_inode_array)->count & EIA_MASK) == EIA_MASK) {
/* expand the array once all 15 + n * 16 slots are full */
struct ext4_xattr_inode_array *new_array = NULL;
- int count = (*ea_inode_array)->count;
+ unsigned int count = (*ea_inode_array)->count;
It seems `count` is not actually needed anymore.
If you remove it and directly use `(*ea_inode_array)->count` in the following
call to `kmalloc()`, you could use `struct_size()` in the call to `memcpy()`
below, and copy the whole thing in one line. See below.
- /* if new_array is NULL, this is essentially offsetof() */
- new_array = kmalloc(
- offsetof(struct ext4_xattr_inode_array,
- inodes[count + EIA_INCR]),
- GFP_NOFS);
+ new_array = kmalloc(struct_size(*ea_inode_array, inodes,
+ count + EIA_INCR),
+ GFP_NOFS);
if (new_array == NULL)
return -ENOMEM;
- memcpy(new_array, *ea_inode_array,
- offsetof(struct ext4_xattr_inode_array, inodes[count]));
+ new_array->count = count;
+ memcpy(new_array->inodes, (*ea_inode_array)->inodes,
+ count * sizeof(struct inode *));
memcpy(new_array, *ea_inode_array, struct_size(new_array, inodes, (*ea_inode_array)->count));
kfree(*ea_inode_array);
*ea_inode_array = new_array;
}
Also, you are missing one more like just below this one, where `(*ea_inode_array)->count`
is currently being used to directly index `inodes`:
(*ea_inode_array)->inodes[(*ea_inode_array)->count++] = inode;
Thanks
--
Gustavo
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index bd97c4aa8177..e14fb19dc912 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -130,8 +130,8 @@ struct ext4_xattr_ibody_find {
};
struct ext4_xattr_inode_array {
- unsigned int count; /* # of used items in the array */
- struct inode *inodes[];
+ unsigned int count;
+ struct inode *inodes[] __counted_by(count);
};
extern const struct xattr_handler ext4_xattr_user_handler;
