mmc: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200226223125.GA20630@embeddedor
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci-acpi.c b/drivers/mmc/host/sdhci-acpi.c
index 2a2173d953f584d283eecc7845147e88d152435e..68cf41747fa56f414ce20f985299b3cf38487f3c 100644 (file)
--- a/drivers/mmc/host/sdhci-acpi.c
+++ b/drivers/mmc/host/sdhci-acpi.c
@@ -75,7 +75,7 @@ struct sdhci_acpi_host {
        bool                            use_runtime_pm;
        bool                            is_intel;
        bool                            reset_signal_volt_on_suspend;
-       unsigned long                   private[0] ____cacheline_aligned;
+       unsigned long                   private[] ____cacheline_aligned;
 };
 
 enum {

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index e573495f872660597b0e96414d0cf501cd8551d3..6da6d4fb5edd79f7eba922b3d2b4bb350b54cbec 100644 (file)
--- a/drivers/mmc/host/sdhci-cadence.c
+++ b/drivers/mmc/host/sdhci-cadence.c
@@ -68,7 +68,7 @@ struct sdhci_cdns_priv {
        void __iomem *hrs_addr;
        bool enhanced_strobe;
        unsigned int nr_phy_params;
-       struct sdhci_cdns_phy_param phy_params[0];
+       struct sdhci_cdns_phy_param phy_params[];
 };
 
 struct sdhci_cdns_phy_cfg {

diff --git a/drivers/mmc/host/sdhci-pci.h b/drivers/mmc/host/sdhci-pci.h
index 981bbbe63aff52265a167a8ea6a173d73eeaf44a..42ccd123b04689e6e1d88632f0b00bce705ef223 100644 (file)
--- a/drivers/mmc/host/sdhci-pci.h
+++ b/drivers/mmc/host/sdhci-pci.h
@@ -163,7 +163,7 @@ struct sdhci_pci_slot {
        bool                    cd_override_level;
 
        void (*hw_reset)(struct sdhci_host *host);
-       unsigned long           private[0] ____cacheline_aligned;
+       unsigned long           private[] ____cacheline_aligned;
 };
 
 struct sdhci_pci_chip {

diff --git a/drivers/mmc/host/sdhci-pltfm.h b/drivers/mmc/host/sdhci-pltfm.h
index 2af445b8c325bd298f9d109eebb132a0f11b7b72..6301b81cf5731b871e1c7d1523e18583d20f0c63 100644 (file)
--- a/drivers/mmc/host/sdhci-pltfm.h
+++ b/drivers/mmc/host/sdhci-pltfm.h
@@ -25,7 +25,7 @@ struct sdhci_pltfm_host {
        unsigned int clock;
        u16 xfer_mode_shadow;
 
-       unsigned long private[0] ____cacheline_aligned;
+       unsigned long private[] ____cacheline_aligned;
 };
 
 #ifdef CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER

diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index cac2d97782e62deb0dbc08429aa00f7c91cc7419..249635692112ae1ff9b408e0419ae28aefee523a 100644 (file)
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -614,7 +614,7 @@ struct sdhci_host {
 
        u64                     data_timeout;
 
-       unsigned long private[0] ____cacheline_aligned;
+       unsigned long private[] ____cacheline_aligned;
 };
 
 struct sdhci_ops {

diff --git a/drivers/mmc/host/vub300.c b/drivers/mmc/host/vub300.c
index 6ced1b7f642fcca59513f98c3cc4df2112f67113..a5a90d133f1f327d6fd7be6e00f736eaba12539d 100644 (file)
--- a/drivers/mmc/host/vub300.c
+++ b/drivers/mmc/host/vub300.c
@@ -95,7 +95,7 @@ struct sd_response_header {
        u8 port_number;
        u8 command_type;
        u8 command_index;
-       u8 command_response[0];
+       u8 command_response[];
 } __packed;
 
 struct sd_status_header {

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index f5db24a6a860801fba6c255aaaa6a11d6e261b08..c318fb5b6a94180926b49bc18920076289226ee5 100644 (file)
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -468,7 +468,7 @@ struct mmc_host {
        /* Host Software Queue support */
        bool                    hsq_enabled;
 
-       unsigned long           private[0] ____cacheline_aligned;
+       unsigned long           private[] ____cacheline_aligned;
 };
 
 struct device_node;

diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index 5a177f7a83c3acc75b1e93daf2ddf9534be9285d..fa2aaab5e57aa5a74cda147a2598a506e0fb4904 100644 (file)
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -25,7 +25,7 @@ struct sdio_func_tuple {
        struct sdio_func_tuple *next;
        unsigned char code;
        unsigned char size;
-       unsigned char data[0];
+       unsigned char data[];
 };
 
 /*

diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h
index 00c08120f3ba60c2719458fd8903dd953744a1df..98e29e7f54ace2f7ca13b1dfd5c337976b2192d9 100644 (file)
--- a/include/uapi/linux/mmc/ioctl.h
+++ b/include/uapi/linux/mmc/ioctl.h
@@ -57,7 +57,7 @@ struct mmc_ioc_cmd {
  */
 struct mmc_ioc_multi_cmd {
        __u64 num_of_cmds;
-       struct mmc_ioc_cmd cmds[0];
+       struct mmc_ioc_cmd cmds[];
 };
 
 #define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)