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afs: Add __counted_by for struct afs_acl and use struct_size()

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Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.

This code was found with the help of Coccinelle, and audited and
fixed manually.

Signed-off-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/ZSVKwBmxQ1amv47E@work
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Gustavo A. R. Silva 2023-10-10 06:59:44 -06:00 committed by Kees Cook
parent 97f3880a33
commit 446425648c
2 changed files with 2 additions and 2 deletions
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2
fs/afs/internal.h
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@ -1116,7 +1116,7 @@ extern void afs_fs_inline_bulk_status(struct afs_operation *);
struct afs_acl { struct afs_acl {
u32 size; u32 size;
u8 data[]; u8 data[] __counted_by(size);
}; };
extern void afs_fs_fetch_acl(struct afs_operation *); extern void afs_fs_fetch_acl(struct afs_operation *);

2
fs/afs/xattr.c
View File

@ -75,7 +75,7 @@ static bool afs_make_acl(struct afs_operation *op,
{ {
struct afs_acl *acl; struct afs_acl *acl;
acl = kmalloc(sizeof(*acl) + size, GFP_KERNEL); acl = kmalloc(struct_size(acl, data, size), GFP_KERNEL);
if (!acl) { if (!acl) {
afs_op_nomem(op); afs_op_nomem(op);
return false; return false;