From 03826bc1fa6c90405bf05831f2b501a8368dcd27 Mon Sep 17 00:00:00 2001 From: Leon Romanovsky Date: Sun, 26 Jul 2026 12:13:55 +0300 Subject: [PATCH] RDMA/mlx5: Fix stack out-of-bounds read in cc_params debugfs get_param() reads a congestion parameter as a u32 but formats it with the signed "%d" into an 11-byte stack buffer. A value with bit 31 set, such as 0x80000000, renders as "-2147483648\n" whose full length is 12. snprintf() stores only 11 bytes yet returns 12, so simple_read_from_buffer() treats 12 bytes as valid and reads one byte past lbuf[]. Size the buffer for the widest unsigned decimal, format with "%u" to match the u32, and use scnprintf() so the length passed to simple_read_from_buffer() reflects the bytes actually stored. Fixes: 4a2da0b8c0782 ("IB/mlx5: Add debug control parameters for congestion control") Link: https://patch.msgid.link/20260726-get-param-leaks-kernel-stack-memory-v1-1-d61a4d39662d@nvidia.com Signed-off-by: Leon Romanovsky --- drivers/infiniband/hw/mlx5/cong.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/hw/mlx5/cong.c b/drivers/infiniband/hw/mlx5/cong.c index 98c90d0dbab4..e91bf278ab97 100644 --- a/drivers/infiniband/hw/mlx5/cong.c +++ b/drivers/infiniband/hw/mlx5/cong.c @@ -389,15 +389,13 @@ static ssize_t get_param(struct file *filp, char __user *buf, size_t count, int offset = param->offset; u32 var = 0; int ret; - char lbuf[11]; + char lbuf[12]; ret = mlx5_ib_get_cc_params(param->dev, param->port_num, offset, &var); if (ret) return ret; - ret = snprintf(lbuf, sizeof(lbuf), "%d\n", var); - if (ret < 0) - return ret; + ret = scnprintf(lbuf, sizeof(lbuf), "%u\n", var); return simple_read_from_buffer(buf, count, pos, lbuf, ret); }