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> > It then allocates the bounce buffer with: > > kmemdup(buf, map_len, GFP_KERNEL); > > kmemdup() copies the full allocation size, causing it to read map_len > bytes from buf even though only len bytes are valid. This results in an > out-of-bounds read of up to cache_line_size() - 1 bytes past the end of > the caller's buffer. > > Fix the issue by allocating the bounce buffer with kzalloc() and copying > only len bytes from the original buffer. The remaining bytes up to > map_len stay zero-filled, avoiding both the out-of-bounds read and > exposure of unrelated memory contents to the DMA engine. > > Fixes: f8d9e56aeb87 ("i3c: master: Add helpers for DMA mapping and bounce buffer handling") > Cc: stable@vger.kernel.org > Signed-off-by: Adrian Hunter > --- Reviewed-by: Frank Li > drivers/i3c/master.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c > index afcd7a21a3e6..f9a6c8560fab 100644 > --- a/drivers/i3c/master.c > +++ b/drivers/i3c/master.c > @@ -2216,12 +2216,11 @@ struct i3c_dma *i3c_master_dma_map_single(struct device *dev, void *buf, > > if (force_bounce) { > dma_xfer->map_len = ALIGN(len, cache_line_size()); > - if (dir == DMA_FROM_DEVICE) > - bounce = kzalloc(dma_xfer->map_len, GFP_KERNEL); > - else > - bounce = kmemdup(buf, dma_xfer->map_len, GFP_KERNEL); > + bounce = kzalloc(dma_xfer->map_len, GFP_KERNEL); > if (!bounce) > return NULL; > + if (dir != DMA_FROM_DEVICE) > + memcpy(bounce, buf, len); > dma_buf = bounce; > } > > -- > 2.53.0 >