4.16-stable review patch. If anyone has any objections, please let me know.
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From: Jack Morgenstein jackm@dev.mellanox.co.il
[ Upstream commit b03bcde962606d2ee59a4e9dd470db9ad53c5418 ]
When the kernel was compiled using the UBSAN option, we saw the following stack trace:
[ 1184.827917] UBSAN: Undefined behaviour in drivers/infiniband/hw/mlx4/mr.c:349:27 [ 1184.828114] signed integer overflow: [ 1184.828247] -2147483648 - 1 cannot be represented in type 'int'
The problem was caused by calling round_up in procedure mlx4_ib_umem_calc_optimal_mtt_size (on line 349, as noted in the stack trace) with the second parameter (1 << block_shift) (which is an int). The second parameter should have been (1ULL << block_shift) (which is an unsigned long long).
(1 << block_shift) is treated by the compiler as an int (because 1 is an integer).
Now, local variable block_shift is initialized to 31. If block_shift is 31, 1 << block_shift is 1 << 31 = 0x80000000=-214748368. This is the most negative int value.
Inside the round_up macro, there is a cast applied to ((1 << 31) - 1). However, this cast is applied AFTER ((1 << 31) - 1) is calculated. Since (1 << 31) is treated as an int, we get the negative overflow identified by UBSAN in the process of calculating ((1 << 31) - 1).
The fix is to change (1 << block_shift) to (1ULL << block_shift) on line 349.
Fixes: 9901abf58368 ("IB/mlx4: Use optimal numbers of MTT entries") Signed-off-by: Jack Morgenstein jackm@dev.mellanox.co.il Signed-off-by: Leon Romanovsky leonro@mellanox.com Signed-off-by: Doug Ledford dledford@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/infiniband/hw/mlx4/mr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/infiniband/hw/mlx4/mr.c +++ b/drivers/infiniband/hw/mlx4/mr.c @@ -346,7 +346,7 @@ int mlx4_ib_umem_calc_optimal_mtt_size(s /* Add to the first block the misalignment that it suffers from. */ total_len += (first_block_start & ((1ULL << block_shift) - 1ULL)); last_block_end = current_block_start + current_block_len; - last_block_aligned_end = round_up(last_block_end, 1 << block_shift); + last_block_aligned_end = round_up(last_block_end, 1ULL << block_shift); total_len += (last_block_aligned_end - last_block_end);
if (total_len & ((1ULL << block_shift) - 1ULL))