media: cec-pin-error-inj: avoid a false-positive Spectre detection

[ Upstream commit a3d71f256c8a8b5d51ea0dfd09cd85ce3a09d9e1 ]

The current logic makes Smatch to false-detect a Spectre variant 1
vulnerability. The problem is that it initializes an u32 indirectly
from user space input.

After trying to write a fixup, after a while I realized that, in
practice, this shouldn't be a problem, as an u32 is initialized
from u8, but it took some time to discover it.

So, do some code cleanup to make it clearer for both humans
and machines about the valid range for "op".

Fix this warning:
	drivers/media/cec/cec-pin-error-inj.c:170 cec_pin_error_inj_parse_line() warn: potential spectre issue 'pin->error_inj_args'

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/cec/cec-pin-error-inj.c b/drivers/media/cec/cec-pin-error-inj.c
index aaa899a175ceca9150b90b0dee058b32d8de4272..1e644a8c1a778f7f051426c5f00ad1dba8992da9 100644 (file)
--- a/drivers/media/cec/cec-pin-error-inj.c
+++ b/drivers/media/cec/cec-pin-error-inj.c
@@ -81,10 +81,9 @@ bool cec_pin_error_inj_parse_line(struct cec_adapter *adap, char *line)
        u64 *error;
        u8 *args;
        bool has_op;
-       u32 op;
+       u8 op;
        u8 mode;
        u8 pos;
-       u8 v;
 
        p = skip_spaces(p);
        token = strsep(&p, delims);
@@ -146,12 +145,18 @@ bool cec_pin_error_inj_parse_line(struct cec_adapter *adap, char *line)
        comma = strchr(token, ',');
        if (comma)
                *comma++ = '\0';
-       if (!strcmp(token, "any"))
-               op = CEC_ERROR_INJ_OP_ANY;
-       else if (!kstrtou8(token, 0, &v))
-               op = v;
-       else
+       if (!strcmp(token, "any")) {
+               has_op = false;
+               error = pin->error_inj + CEC_ERROR_INJ_OP_ANY;
+               args = pin->error_inj_args[CEC_ERROR_INJ_OP_ANY];
+       } else if (!kstrtou8(token, 0, &op)) {
+               has_op = true;
+               error = pin->error_inj + op;
+               args = pin->error_inj_args[op];
+       } else {
                return false;
+       }
+
        mode = CEC_ERROR_INJ_MODE_ONCE;
        if (comma) {
                if (!strcmp(comma, "off"))
@@ -166,10 +171,6 @@ bool cec_pin_error_inj_parse_line(struct cec_adapter *adap, char *line)
                        return false;
        }
 
-       error = pin->error_inj + op;
-       args = pin->error_inj_args[op];
-       has_op = op <= 0xff;
-
        token = strsep(&p, delims);
        if (p) {
                p = skip_spaces(p);