nvmem: rmem: make ->reg_read() straight forward code

memory_read_from_buffer() is a weird choice; it:
 - is made for iteration with ppos a pointer.
 - does futile error checking in our case.
 - does NOT ensure we read exactly N bytes.

Replace it by:
1. A check that (offset + bytes) lands inside the region and,
2. a plain memcpy().

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20241230143035.265518-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c
index 7f907c5a445e7865c8626e00362df0040fe52241..0dc5c8237c7538efe4597c182d7bdb709b945851 100644 (file)
--- a/drivers/nvmem/rmem.c
+++ b/drivers/nvmem/rmem.c
@@ -21,10 +21,10 @@ static int rmem_read(void *context, unsigned int offset,
                     void *val, size_t bytes)
 {
        struct rmem *priv = context;
-       size_t available = priv->mem->size;
-       loff_t off = offset;
        void *addr;
-       int count;
+
+       if ((phys_addr_t)offset + bytes > priv->mem->size)
+               return -EIO;
 
        /*
         * Only map the reserved memory at this point to avoid potential rogue
@@ -36,20 +36,17 @@ static int rmem_read(void *context, unsigned int offset,
         * An alternative would be setting the memory as RO, set_memory_ro(),
         * but as of Dec 2020 this isn't possible on arm64.
         */
-       addr = memremap(priv->mem->base, available, MEMREMAP_WB);
+       addr = memremap(priv->mem->base, priv->mem->size, MEMREMAP_WB);
        if (!addr) {
                dev_err(priv->dev, "Failed to remap memory region\n");
                return -ENOMEM;
        }
 
-       count = memory_read_from_buffer(val, bytes, &off, addr, available);
+       memcpy(val, addr + offset, bytes);
 
        memunmap(addr);
 
-       if (count < 0)
-               return count;
-
-       return count == bytes ? 0 : -EIO;
+       return 0;
 }
 
 static int rmem_probe(struct platform_device *pdev)