On 9/19/21 04:46, 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. > > In this case this is not actually dynamic size: all the operands > involved in the calculation are constant values. However it is best to > refactor this anyway, just to keep the open-coded math idiom out of > code. > > So, use the struct_size() helper to do the arithmetic instead of the > argument "size + count * size" 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@xxxxxxx> > --- > fs/fs-writeback.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 81ec192ce067..f7abff31e026 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -624,8 +624,8 @@ bool cleanup_offline_cgwb(struct bdi_writeback *wb) > int nr; > bool restart = false; > > - isw = kzalloc(sizeof(*isw) + WB_MAX_INODES_PER_ISW * > - sizeof(struct inode *), GFP_KERNEL); > + isw = kzalloc(struct_size(isw, inodes, WB_MAX_INODES_PER_ISW), > + GFP_KERNEL); There is another instance at: 569 isw = kzalloc(sizeof(*isw) + 2 * sizeof(struct inode *), GFP_ATOMIC); 570 if (!isw) 571 return; If you are finding these with the help of Coccinelle, please mention it in the changelog text. :) Thanks -- Gustavo > if (!isw) > return restart; > > -- > 2.25.1 >
