From ac7110d883ff2a25d2b0ae45c909c02d598c33af Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Tue, 10 Oct 2023 06:46:50 -0600 Subject: [PATCH] atags_proc: Add __counted_by for struct buffer and use struct_size() 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 Reviewed-by: Kees Cook Reviewed-by: Justin Stitt Link: https://lore.kernel.org/r/ZSVHurzo/4aFQcT3@work Signed-off-by: Kees Cook --- arch/arm/kernel/atags_proc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/atags_proc.c b/arch/arm/kernel/atags_proc.c index 3ec2afe78423..cd09f8ab93e3 100644 --- a/arch/arm/kernel/atags_proc.c +++ b/arch/arm/kernel/atags_proc.c @@ -7,7 +7,7 @@ struct buffer { size_t size; - char data[]; + char data[] __counted_by(size); }; static ssize_t atags_read(struct file *file, char __user *buf, @@ -54,7 +54,7 @@ static int __init init_atags_procfs(void) WARN_ON(tag->hdr.tag != ATAG_NONE); - b = kmalloc(sizeof(*b) + size, GFP_KERNEL); + b = kmalloc(struct_size(b, data, size), GFP_KERNEL); if (!b) goto nomem;