Messages in this thread | | | Date | Tue, 10 Oct 2023 15:53:28 -0700 | From | Kees Cook <> | Subject | Re: [PATCH][next] afs: Add __counted_by for struct afs_acl and use struct_size() |
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On Tue, Oct 10, 2023 at 06:59:44AM -0600, Gustavo A. R. Silva wrote: > 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> > --- > fs/afs/internal.h | 2 +- > fs/afs/xattr.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/afs/internal.h b/fs/afs/internal.h > index 469a717467a4..e263a58b82ba 100644 > --- a/fs/afs/internal.h > +++ b/fs/afs/internal.h > @@ -1116,7 +1116,7 @@ extern void afs_fs_inline_bulk_status(struct afs_operation *); > > struct afs_acl { > u32 size; > - u8 data[]; > + u8 data[] __counted_by(size); > };
It's surprising how many of these 2-member structs we have in the kernel that do the same basic thing. :)
And I see that "size" is assigned before using "data", good.
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
-- Kees Cook
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