| Message ID | 20240123002814.1396804-37-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
On Mon, Jan 22, 2024 at 04:27:12PM -0800, Kees Cook wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Benjamin LaHaise <bcrl@kvack.org> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Christian Brauner <brauner@kernel.org> > Cc: Jan Kara <jack@suse.cz> > Cc: linux-aio@kvack.org > Cc: linux-fsdevel@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- What's the plan? Merge the generic infrastructure and we can pick the individual patches?
On Mon 22-01-24 16:27:12, Kees Cook wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Benjamin LaHaise <bcrl@kvack.org> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Christian Brauner <brauner@kernel.org> > Cc: Jan Kara <jack@suse.cz> > Cc: linux-aio@kvack.org > Cc: linux-fsdevel@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/aio.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/aio.c b/fs/aio.c > index bb2ff48991f3..edd19be3f4b1 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -796,7 +796,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) > /* limit the number of system wide aios */ > spin_lock(&aio_nr_lock); > if (aio_nr + ctx->max_reqs > aio_max_nr || > - aio_nr + ctx->max_reqs < aio_nr) { > + add_would_overflow(aio_nr, ctx->max_reqs)) { > spin_unlock(&aio_nr_lock); > err = -EAGAIN; > goto err_ctx; > -- > 2.34.1 >
diff --git a/fs/aio.c b/fs/aio.c index bb2ff48991f3..edd19be3f4b1 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -796,7 +796,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) /* limit the number of system wide aios */ spin_lock(&aio_nr_lock); if (aio_nr + ctx->max_reqs > aio_max_nr || - aio_nr + ctx->max_reqs < aio_nr) { + add_would_overflow(aio_nr, ctx->max_reqs)) { spin_unlock(&aio_nr_lock); err = -EAGAIN; goto err_ctx;
In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: linux-aio@kvack.org Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/aio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)