From 4c26dea1c096138b6e7c49c4886e68fbf6013217 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 18 Dec 2023 18:24:53 -0600 Subject: [PATCH] bcachefs: Replace zero-length array with flex-array member and use __counted_by Fake flexible arrays (zero-length and one-element arrays) are deprecated, and should be replaced by flexible-array members. So, replace zero-length array with a flexible-array member in `struct bch_ioctl_fsck_offline`. Also annotate array `devs` with `__counted_by()` to 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). This fixes the following -Warray-bounds warnings: fs/bcachefs/chardev.c: In function 'bch2_ioctl_fsck_offline': fs/bcachefs/chardev.c:363:34: warning: array subscript 0 is outside array bounds of '__u64[0]' {aka 'long long unsigned int[]'} [-Warray-bounds=] 363 | if (copy_from_user(devs, &user_arg->devs[0], sizeof(user_arg->devs[0]) * arg.nr_devs)) { | ^~~~~~~~~~~~~~~~~~ In file included from fs/bcachefs/chardev.c:5: fs/bcachefs/bcachefs_ioctl.h:400:33: note: while referencing 'devs' 400 | __u64 devs[0]; This results in no differences in binary output. Signed-off-by: Gustavo A. R. Silva Signed-off-by: Kent Overstreet --- fs/bcachefs/bcachefs_ioctl.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/bcachefs/bcachefs_ioctl.h b/fs/bcachefs/bcachefs_ioctl.h index 21f81b16f24e..4b8fba754b1c 100644 --- a/fs/bcachefs/bcachefs_ioctl.h +++ b/fs/bcachefs/bcachefs_ioctl.h @@ -397,7 +397,7 @@ struct bch_ioctl_fsck_offline { __u64 flags; __u64 opts; /* string */ __u64 nr_devs; - __u64 devs[0]; + __u64 devs[] __counted_by(nr_devs); }; /* -- 2.39.5