| Message ID | 20230623211457.102544-11-Julia.Lawall@inria.fr |
|---|---|
| State | New |
| Headers | show |
| Series | use array_size | expand |
On 6/23/2023 3:14 PM, Julia Lawall wrote: > Use array_size to protect against multiplication overflows. > > The changes were done using the following Coccinelle semantic patch: > > // <smpl> > @@ > expression E1, E2; > constant C1, C2; > identifier alloc = {vmalloc,vzalloc}; > @@ > > ( > alloc(C1 * C2,...) > | > alloc( > - (E1) * (E2) > + array_size(E1, E2) > ,...) > ) > // </smpl> > > Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> > > --- > drivers/bus/mhi/host/init.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c > index f72fcb66f408..34a543a67068 100644 > --- a/drivers/bus/mhi/host/init.c > +++ b/drivers/bus/mhi/host/init.c > @@ -759,8 +759,8 @@ static int parse_ch_cfg(struct mhi_controller *mhi_cntrl, > * so to avoid any memory possible allocation failures, vzalloc is > * used here > */ > - mhi_cntrl->mhi_chan = vzalloc(mhi_cntrl->max_chan * > - sizeof(*mhi_cntrl->mhi_chan)); > + mhi_cntrl->mhi_chan = vzalloc(array_size(mhi_cntrl->max_chan, > + sizeof(*mhi_cntrl->mhi_chan))); > if (!mhi_cntrl->mhi_chan) > return -ENOMEM; > > > This doesn't seem like a good fix. If we've overflowed the multiplication, I don't think we should continue, and the function should return an error. array_size() is going to return SIZE_MAX, and it looks like it is possible that vzalloc() may be able to allocate that successfully in some scenarios. However, that is going to be less memory than parse_ch_cfg() expected to allocate, so later on I expect the function will still corrupt memory - basically the same result as what the unchecked overflow would do. I'm not convinced the semantic patch is bringing value as I suspect most of the code being patched is in the same situation. -Jeff
On Fri, 23 Jun 2023, Jeffrey Hugo wrote: > On 6/23/2023 3:14 PM, Julia Lawall wrote: > > Use array_size to protect against multiplication overflows. > > > > The changes were done using the following Coccinelle semantic patch: > > > > // <smpl> > > @@ > > expression E1, E2; > > constant C1, C2; > > identifier alloc = {vmalloc,vzalloc}; > > @@ > > ( > > alloc(C1 * C2,...) > > | > > alloc( > > - (E1) * (E2) > > + array_size(E1, E2) > > ,...) > > ) > > // </smpl> > > > > Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> > > > > --- > > drivers/bus/mhi/host/init.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c > > index f72fcb66f408..34a543a67068 100644 > > --- a/drivers/bus/mhi/host/init.c > > +++ b/drivers/bus/mhi/host/init.c > > @@ -759,8 +759,8 @@ static int parse_ch_cfg(struct mhi_controller > > *mhi_cntrl, > > * so to avoid any memory possible allocation failures, vzalloc is > > * used here > > */ > > - mhi_cntrl->mhi_chan = vzalloc(mhi_cntrl->max_chan * > > - sizeof(*mhi_cntrl->mhi_chan)); > > + mhi_cntrl->mhi_chan = vzalloc(array_size(mhi_cntrl->max_chan, > > + sizeof(*mhi_cntrl->mhi_chan))); > > if (!mhi_cntrl->mhi_chan) > > return -ENOMEM; > > > > > > This doesn't seem like a good fix. > > If we've overflowed the multiplication, I don't think we should continue, and > the function should return an error. array_size() is going to return > SIZE_MAX, and it looks like it is possible that vzalloc() may be able to > allocate that successfully in some scenarios. However, that is going to be > less memory than parse_ch_cfg() expected to allocate, so later on I expect the > function will still corrupt memory - basically the same result as what the > unchecked overflow would do. > > I'm not convinced the semantic patch is bringing value as I suspect most of > the code being patched is in the same situation. OK, this just brings the code in line with all the calls updated by Kees's original patch, cited in the cover letter, which were all the calls containing a multiplication that existed at the time. 42bc47b35320 ("treewide: Use array_size() in vmalloc()") fad953ce0b22 ("treewide: Use array_size() in vzalloc()") julia > > -Jeff >
On Fri, Jun 23, 2023 at 04:09:46PM -0600, Jeffrey Hugo wrote: > Kees, would you please chime in and educate me here? I feel like I'm > missing something important here. The array_size() family will saturate at SIZE_MAX (rather than potentially wrapping around). No allocator can fulfil a 18446744073709551615 byte (18 exabyte) allocation. :) So the NULL return value will (hopefully) trigger an error path.
On 6/23/2023 3:14 PM, Julia Lawall wrote: > Use array_size to protect against multiplication overflows. > > The changes were done using the following Coccinelle semantic patch: > > // <smpl> > @@ > expression E1, E2; > constant C1, C2; > identifier alloc = {vmalloc,vzalloc}; > @@ > > ( > alloc(C1 * C2,...) > | > alloc( > - (E1) * (E2) > + array_size(E1, E2) > ,...) > ) > // </smpl> > > Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> > Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com> Tested-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c index f72fcb66f408..34a543a67068 100644 --- a/drivers/bus/mhi/host/init.c +++ b/drivers/bus/mhi/host/init.c @@ -759,8 +759,8 @@ static int parse_ch_cfg(struct mhi_controller *mhi_cntrl, * so to avoid any memory possible allocation failures, vzalloc is * used here */ - mhi_cntrl->mhi_chan = vzalloc(mhi_cntrl->max_chan * - sizeof(*mhi_cntrl->mhi_chan)); + mhi_cntrl->mhi_chan = vzalloc(array_size(mhi_cntrl->max_chan, + sizeof(*mhi_cntrl->mhi_chan))); if (!mhi_cntrl->mhi_chan) return -ENOMEM;
Use array_size to protect against multiplication overflows. The changes were done using the following Coccinelle semantic patch: // <smpl> @@ expression E1, E2; constant C1, C2; identifier alloc = {vmalloc,vzalloc}; @@ ( alloc(C1 * C2,...) | alloc( - (E1) * (E2) + array_size(E1, E2) ,...) ) // </smpl> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> --- drivers/bus/mhi/host/init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)