3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
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
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Signed-off-by: Doug Ledford dledford@redhat.com [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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> @@ -1116,6 +1118,7 @@ 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;