In case MMIO size is bigger than 4G and peer2peer DMA goes
through host bridge, we trigger a code path that assigns the
total linked IOVA (which is greater than 4G) to mapped_len.
Previously, `mapped_len` was declared as 32-bit `unsigned int`.
When accumulating `size_t` lengths, this leads to a silent wrap-around.
This truncation causes truncated lengths to be passed to functions
like `fill_sg_entry()`.
Fix this by changing `mapped_len` to `size_t` (64-bit). While
at it, fix similar potential overflow issues in `calc_sg_nents`
by using `check_add_overflow()` for `nents` and using
`unsigned int` for the loop iterator in `fill_sg_entry` to match.
Fixes: 3aa31a8bb11e ("dma-buf: provide phys_vec to scatter-gather mapping
routine")
Cc: [email protected]
Cc: [email protected]
Reviewed-by: Pranjal Shrivastava <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: David Hu <[email protected]>
---
Changes in v7:
- Added a missing blank line after local variable declaration in
`calc_sg_nents()` (Leon).
- Collected Reviewed-by from Leon Romanovsky.
Changes in v6:
- Used `check_add_overflow()` in `calc_sg_nents()` for safer
accumulation (Leon).
- Dropped explicit `!nents` check and added a comment noting that
`sg_alloc_table` handles `nents == 0` (Leon).
- Collected Reviewed-by from Kevin Tian.
Changes in v5:
- Removed WARN_ON_ONCE from calc_sg_nents() to avoid log noise (Jason).
- Added explicit check for `!nents` in dma_buf_phys_vec_to_sgt() to
cleanly return -EINVAL on overflow (Jason).
Changes in v4:
- Added WARN_ON_ONCE() to the nents overflow check to prevent silent
failures (Claude Bot).
Changes in v3:
- Removed leftover sentence fragment from the commit message.
- Kept `nents = 0` initialization (previously stated as removed in the
v2 changelog) as it is strictly required for the `+=` accumulation
loop in `calc_sg_nents()`.
Changes in v2:
- Fixed 'IVOA' -> 'IOVA' typo and expanded commit message (Claude Bot).
- Added Reverse Xmas tree formatting (Pranjal).
- Folded in extra bounds checking for calc_sg_nents() (Pranjal).
- Folded in type consistency fix for fill_sg_entry() (Pranjal).
- Collected Reviewed-by from Pranjal Shrivastava.
drivers/dma-buf/dma-buf-mapping.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/drivers/dma-buf/dma-buf-mapping.c
b/drivers/dma-buf/dma-buf-mapping.c
index 794acff2546a..80f6ab2f4809 100644
--- a/drivers/dma-buf/dma-buf-mapping.c
+++ b/drivers/dma-buf/dma-buf-mapping.c
@@ -5,12 +5,13 @@
*/
#include <linux/dma-buf-mapping.h>
#include <linux/dma-resv.h>
+#include <linux/overflow.h>
static struct scatterlist *fill_sg_entry(struct scatterlist *sgl, size_t
length,
dma_addr_t addr)
{
unsigned int len, nents;
- int i;
+ unsigned int i;
nents = DIV_ROUND_UP(length, UINT_MAX);
for (i = 0; i < nents; i++) {
@@ -40,8 +41,12 @@ static unsigned int calc_sg_nents(struct dma_iova_state
*state,
size_t i;
if (!state || !dma_use_iova(state)) {
- for (i = 0; i < nr_ranges; i++)
- nents += DIV_ROUND_UP(phys_vec[i].len, UINT_MAX);
+ for (i = 0; i < nr_ranges; i++) {
+ unsigned int added = DIV_ROUND_UP(phys_vec[i].len,
UINT_MAX);
+
+ if (check_add_overflow(nents, added, &nents))
+ return 0;
+ }
} else {
/*
* In IOVA case, there is only one SG entry which spans
@@ -95,9 +100,10 @@ struct sg_table *dma_buf_phys_vec_to_sgt(struct
dma_buf_attachment *attach,
size_t nr_ranges, size_t size,
enum dma_data_direction dir)
{
- unsigned int nents, mapped_len = 0;
struct dma_buf_dma *dma;
struct scatterlist *sgl;
+ size_t mapped_len = 0;
+ unsigned int nents;
dma_addr_t addr;
size_t i;
int ret;
@@ -133,6 +139,8 @@ struct sg_table *dma_buf_phys_vec_to_sgt(struct
dma_buf_attachment *attach,
}
nents = calc_sg_nents(dma->state, phys_vec, nr_ranges, size);
+
+ /* sg_alloc_table will cleanly fail and return -EINVAL if nents == 0 */
ret = sg_alloc_table(&dma->sgt, nents, GFP_KERNEL | __GFP_ZERO);
if (ret)
goto err_free_state;
--
2.54.0.1064.gd145956f57-goog
