| Message ID | ZSVHurzo/4aFQcT3@work (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [next] atags_proc: Add __counted_by for struct buffer and use struct_size() | expand |
On Tue, Oct 10, 2023 at 5:47 AM Gustavo A. R. Silva <gustavoars@kernel.org> 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> Looks good to me. Reviewed-by: Justin Stitt <justinstitt@google.com> > --- > 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; > > -- > 2.34.1 > > Thanks Justin
On Tue, Oct 10, 2023 at 06:46:50AM -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> > --- > 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; > Yup, "size" is assigned before accessing "data". Reviewed-by: Kees Cook <keescook@chromium.org>
On Tue, 10 Oct 2023 06:46:50 -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. > > [...] Applied to for-next/hardening, thanks! [1/1] atags_proc: Add __counted_by for struct buffer and use struct_size() https://git.kernel.org/kees/c/ac7110d883ff Take care,
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;
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> --- arch/arm/kernel/atags_proc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)