platform/x86/amd/hsmp: Clamp ioctl/send_message indices (Spectre v1)

Although validate_message() checks msg_id, a mispredicted branch can
still allow speculative indexing into hsmp_msg_desc_table[]. Clamp
msg.msg_id with array_index_nospec() at entry to hsmp_ioctl_msg() so
downstream dereferences (including via is_get_msg() and
hsmp_send_message()) see a bounded index.

Similarly, hsmp_send_message() bounds-checks msg->sock_ind before
indexing hsmp_pdev.sock[], but a mispredicted branch can still
speculatively use the raw index (Spectre v1, CVE-2017-5753). Apply
array_index_nospec() after the check so every caller that reaches
hsmp_pdev.sock[] through this helper sees a clamped socket
index—including hsmp_ioctl_msg() and any other path that hands a
user-derived struct hsmp_message to hsmp_send_message().

Reviewed-by: Muthusamy Ramalingam <muthusamy.ramalingam@amd.com>
Signed-off-by: Muralidhara M K <muralidhara.mk@amd.com>
Link: https://patch.msgid.link/20260612042610.1629037-7-muralidhara.mk@amd.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c
index 631ffc0978d16d935de707acfa11653ae46bf4aa..6a26937fc2b5857bafa34f174162ae865455185f 100644 (file)
--- a/drivers/platform/x86/amd/hsmp/hsmp.c
+++ b/drivers/platform/x86/amd/hsmp/hsmp.c
@@ -202,6 +202,7 @@ static int validate_message(struct hsmp_message *msg)
 int hsmp_send_message(struct hsmp_message *msg)
 {
        struct hsmp_socket *sock;
+       unsigned int sock_ind;
        int ret;
 
        if (!msg)
@@ -212,7 +213,15 @@ int hsmp_send_message(struct hsmp_message *msg)
 
        if (!hsmp_pdev.sock || msg->sock_ind >= hsmp_pdev.num_sockets)
                return -ENODEV;
-       sock = &hsmp_pdev.sock[msg->sock_ind];
+
+       /*
+        * Sanitize sock_ind after the bounds check.  A mispredicted branch can
+        * still let the CPU speculatively use msg->sock_ind as an index into
+        * hsmp_pdev.sock[] (Spectre v1, CVE-2017-5753), including for callers
+        * other than hsmp_ioctl_msg() that pass a user-derived socket index.
+        */
+       sock_ind = array_index_nospec(msg->sock_ind, hsmp_pdev.num_sockets);
+       sock = &hsmp_pdev.sock[sock_ind];
 
        ret = down_interruptible(&sock->hsmp_sem);
        if (ret < 0)
@@ -308,6 +317,19 @@ long hsmp_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
        if (msg.msg_id < HSMP_TEST || msg.msg_id >= HSMP_MSG_ID_MAX)
                return -ENOMSG;
 
+       /*
+        * Sanitize the user-controlled msg_id against speculative
+        * execution.  The bounds check above retires the out-of-range
+        * case with -ENOMSG, but a mispredicted branch can still let the
+        * CPU speculatively use msg_id as an index into
+        * hsmp_msg_desc_table[] (here and in validate_message() /
+        * is_get_msg() called downstream via hsmp_send_message()), and
+        * pull arbitrary kernel memory into the cache (Spectre v1,
+        * CVE-2017-5753).  Clamp once into msg.msg_id so every downstream
+        * dereference sees the sanitized value.
+        */
+       msg.msg_id = array_index_nospec(msg.msg_id, HSMP_MSG_ID_MAX);
+
        switch (fp->f_mode & (FMODE_WRITE | FMODE_READ)) {
        case FMODE_WRITE:
                /*