4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> commit 0295e39595e1146522f2722715dba7f7fba42217 upstream. hdr.cmd can be indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: drivers/infiniband/core/ucm.c:1127 ib_ucm_write() warn: potential spectre issue 'ucm_cmd_table' [r] (local cap) Fix this by sanitizing hdr.cmd before using it to index ucm_cmd_table. Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/infiniband/core/ucm.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/infiniband/core/ucm.c +++ b/drivers/infiniband/core/ucm.c @@ -46,6 +46,8 @@ #include <linux/mutex.h> #include <linux/slab.h> +#include <linux/nospec.h> + #include <asm/uaccess.h> #include <rdma/ib.h> @@ -1115,6 +1117,7 @@ static ssize_t ib_ucm_write(struct file if (hdr.cmd >= ARRAY_SIZE(ucm_cmd_table)) return -EINVAL; + hdr.cmd = array_index_nospec(hdr.cmd, ARRAY_SIZE(ucm_cmd_table)); if (hdr.in + sizeof(hdr) > len) return -EINVAL;
