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[2/5] farsync: fix off-by-one bug in fst_add_one

Message ID 1457965120-3155420-3-git-send-email-arnd@arndb.de
State Accepted
Commit e725a66c0202b5f36c2f9d59d26a65c53bbf21f7
Headers show
Series [1/5] mlx4: add missing braces in verify_qp_parameters | expand

Commit Message

Arnd Bergmann March 14, 2016, 2:18 p.m. UTC
gcc-6 finds an out of bounds access in the fst_add_one function
when calculating the end of the mmio area:

drivers/net/wan/farsync.c: In function 'fst_add_one':
drivers/net/wan/farsync.c:418:53: error: index 2 denotes an offset greater than size of 'u8[2][8192] {aka unsigned char[2][8192]}' [-Werror=array-bounds]
 #define BUF_OFFSET(X)   (BFM_BASE + offsetof(struct buf_window, X))
                                                     ^
include/linux/compiler-gcc.h:158:21: note: in definition of macro '__compiler_offsetof'
  __builtin_offsetof(a, b)
                     ^
drivers/net/wan/farsync.c:418:37: note: in expansion of macro 'offsetof'
 #define BUF_OFFSET(X)   (BFM_BASE + offsetof(struct buf_window, X))
                                     ^~~~~~~~
drivers/net/wan/farsync.c:2519:36: note: in expansion of macro 'BUF_OFFSET'
                                  + BUF_OFFSET ( txBuffer[i][NUM_TX_BUFFER][0]);
                                    ^~~~~~~~~~

The warning is correct, but not critical because this appears
to be a write-only variable that is set by each WAN driver but
never accessed afterwards.

I'm taking the minimal fix here, using the correct pointer by
pointing 'mem_end' to the last byte inside of the register area
as all other WAN drivers do, rather than the first byte outside of
it. An alternative would be to just remove the mem_end member
entirely.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 drivers/net/wan/farsync.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.7.0
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Patch

diff --git a/drivers/net/wan/farsync.c b/drivers/net/wan/farsync.c
index 44541dbc5c28..69b994f3b8c5 100644
--- a/drivers/net/wan/farsync.c
+++ b/drivers/net/wan/farsync.c
@@ -2516,7 +2516,7 @@  fst_add_one(struct pci_dev *pdev, const struct pci_device_id *ent)
                 dev->mem_start   = card->phys_mem
                                  + BUF_OFFSET ( txBuffer[i][0][0]);
                 dev->mem_end     = card->phys_mem
-                                 + BUF_OFFSET ( txBuffer[i][NUM_TX_BUFFER][0]);
+                                 + BUF_OFFSET ( txBuffer[i][NUM_TX_BUFFER - 1][LEN_RX_BUFFER - 1]);
                 dev->base_addr   = card->pci_conf;
                 dev->irq         = card->irq;