On 30/07/24 14:55, 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().
Use struct_size() instead of offsetof() and remove the local variable
count.
Increment count before adding a new inode to the inodes array.
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/
Changes in v3:
- Use struct_size() instead of struct_size_t() as suggested by Kees Cook
- Remove the local variable count as suggested by Gustavo A. R. Silva
- Increment count before adding a new inode as suggested by Gustavo
- Link to v2: https://lore.kernel.org/linux-kernel/20240730172301.231867-4-thorsten.blum@xxxxxxxxxx/
---
fs/ext4/xattr.c | 24 +++++++++++-------------
fs/ext4/xattr.h | 4 ++--
2 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 46ce2f21fef9..4e20ef7cc502 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2879,33 +2879,31 @@ 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]),
- GFP_NOFS);
+ (*ea_inode_array) = kmalloc(
+ struct_size(*ea_inode_array, inodes, EIA_MASK),
+ GFP_NOFS);
if (*ea_inode_array == NULL)
return -ENOMEM;
(*ea_inode_array)->count = 0;
} 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;
- /* if new_array is NULL, this is essentially offsetof() */
new_array = kmalloc(
- offsetof(struct ext4_xattr_inode_array,
- inodes[count + EIA_INCR]),
- GFP_NOFS);
+ struct_size(*ea_inode_array, inodes,
+ (*ea_inode_array)->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 = (*ea_inode_array)->count;
The line above is not really necessary if you copy `*ea_inode_array` at once like
memcpy(... , struct_size(new_array, inodes, (*ea_inode_array)->count));
or like
memcpy(... , struct_size(*ea_inode_array, inodes, (*ea_inode_array)->count));
whichever works.
+ memcpy(new_array, *ea_inode_array,
+ struct_size(new_array, inodes, new_array->count));
kfree(*ea_inode_array);
*ea_inode_array = new_array;
}
- (*ea_inode_array)->inodes[(*ea_inode_array)->count++] = inode;
+ (*ea_inode_array)->count++;
+ (*ea_inode_array)->inodes[(*ea_inode_array)->count - 1] = inode;
This looks good, thanks!
return 0;
}
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;
--
Gustavo
