pci: Sanity check mask argument to pci_set_*_by_mask()

Coverity complains that in functions like pci_set_word_by_mask()
we might end up shifting by more than 31 bits. This is true,
but only if the caller passes in a zero mask. Help Coverity out
by asserting that the mask argument is valid.

Fixes: CID 1487168

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220818135421.2515257-3-peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index c79144b..97937cc 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -688,7 +688,10 @@ static inline void
 pci_set_byte_by_mask(uint8_t *config, uint8_t mask, uint8_t reg)
 {
     uint8_t val = pci_get_byte(config);
-    uint8_t rval = reg << ctz32(mask);
+    uint8_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_byte(config, (~mask & val) | (mask & rval));
 }
 
@@ -696,7 +699,10 @@ static inline void
 pci_set_word_by_mask(uint8_t *config, uint16_t mask, uint16_t reg)
 {
     uint16_t val = pci_get_word(config);
-    uint16_t rval = reg << ctz32(mask);
+    uint16_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_word(config, (~mask & val) | (mask & rval));
 }
 
@@ -704,7 +710,10 @@ static inline void
 pci_set_long_by_mask(uint8_t *config, uint32_t mask, uint32_t reg)
 {
     uint32_t val = pci_get_long(config);
-    uint32_t rval = reg << ctz32(mask);
+    uint32_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_long(config, (~mask & val) | (mask & rval));
 }
 
@@ -712,7 +721,10 @@ static inline void
 pci_set_quad_by_mask(uint8_t *config, uint64_t mask, uint64_t reg)
 {
     uint64_t val = pci_get_quad(config);
-    uint64_t rval = reg << ctz32(mask);
+    uint64_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_quad(config, (~mask & val) | (mask & rval));
 }