| Message ID | 20210919094432.30510-1-len.baker@gmx.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | cc68c613d6eeac921e6ef5987db5c764858fab1c |
| Delegated to: | Gustavo A. R. Silva |
| Headers | show |
| Series | afs: Prefer struct_size over open coded arithmetic | expand |
On 9/19/21 04:44, Len Baker wrote: > As noted in the "Deprecated Interfaces, Language Features, Attributes, > and Conventions" documentation [1], size calculations (especially > multiplication) should not be performed in memory allocator (or similar) > function arguments due to the risk of them overflowing. This could lead > to values wrapping around and a smaller allocation being made than the > caller was expecting. Using those allocations could lead to linear > overflows of heap memory and other misbehaviors. > > So, use the struct_size() helper to do the arithmetic instead of the > argument "size + size * count" in the kzalloc() function. > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > Signed-off-by: Len Baker <len.baker@gmx.com> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks -- Gustavo > --- > fs/afs/security.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/fs/afs/security.c b/fs/afs/security.c > index 3c7a8fc4f93f..7c6a63a30394 100644 > --- a/fs/afs/security.c > +++ b/fs/afs/security.c > @@ -219,8 +219,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key, > * yet. > */ > size++; > - new = kzalloc(sizeof(struct afs_permits) + > - sizeof(struct afs_permit) * size, GFP_NOFS); > + new = kzalloc(struct_size(new, permits, size), GFP_NOFS); > if (!new) > goto out_put; > > -- > 2.25.1 >
On Mon, Sep 20, 2021 at 07:09:38PM -0500, Gustavo A. R. Silva wrote: > > > On 9/19/21 04:44, Len Baker wrote: > > As noted in the "Deprecated Interfaces, Language Features, Attributes, > > and Conventions" documentation [1], size calculations (especially > > multiplication) should not be performed in memory allocator (or similar) > > function arguments due to the risk of them overflowing. This could lead > > to values wrapping around and a smaller allocation being made than the > > caller was expecting. Using those allocations could lead to linear > > overflows of heap memory and other misbehaviors. > > > > So, use the struct_size() helper to do the arithmetic instead of the > > argument "size + size * count" in the kzalloc() function. > > > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > > > Signed-off-by: Len Baker <len.baker@gmx.com> > > Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> I'm taking this in my -next tree. Thanks, Len. -- Gustavo
Len Baker <len.baker@gmx.com> wrote: > As noted in the "Deprecated Interfaces, Language Features, Attributes, > and Conventions" documentation [1], size calculations (especially > multiplication) should not be performed in memory allocator (or similar) > function arguments due to the risk of them overflowing. This could lead > to values wrapping around and a smaller allocation being made than the > caller was expecting. Using those allocations could lead to linear > overflows of heap memory and other misbehaviors. > > So, use the struct_size() helper to do the arithmetic instead of the > argument "size + size * count" in the kzalloc() function. > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > Signed-off-by: Len Baker <len.baker@gmx.com> Acked-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/security.c b/fs/afs/security.c index 3c7a8fc4f93f..7c6a63a30394 100644 --- a/fs/afs/security.c +++ b/fs/afs/security.c @@ -219,8 +219,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key, * yet. */ size++; - new = kzalloc(sizeof(struct afs_permits) + - sizeof(struct afs_permit) * size, GFP_NOFS); + new = kzalloc(struct_size(new, permits, size), GFP_NOFS); if (!new) goto out_put;
As noted in the "Deprecated Interfaces, Language Features, Attributes, and Conventions" documentation [1], size calculations (especially multiplication) should not be performed in memory allocator (or similar) function arguments due to the risk of them overflowing. This could lead to values wrapping around and a smaller allocation being made than the caller was expecting. Using those allocations could lead to linear overflows of heap memory and other misbehaviors. So, use the struct_size() helper to do the arithmetic instead of the argument "size + size * count" in the kzalloc() function. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments Signed-off-by: Len Baker <len.baker@gmx.com> --- fs/afs/security.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) -- 2.25.1