Re: [PATCH 01/13] firmware_loader: EFI firmware loader must handle pre-allocated buffer

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On 2020-07-17 10:42 a.m., Kees Cook wrote:
The EFI platform firmware fallback would clobber any pre-allocated
buffers. Instead, correctly refuse to reallocate when too small (as
already done in the sysfs fallback), or perform allocation normally
when needed.

Fixes: e4c2c0ff00ec ("firmware: Add new platform fallback mechanism and firm ware_request_platform()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
---
To aid in backporting, this change is made before moving
kernel_read_file() to separate header/source files.
---
  drivers/base/firmware_loader/fallback_platform.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/base/firmware_loader/fallback_platform.c b/drivers/base/firmware_loader/fallback_platform.c
index cdd2c9a9f38a..685edb7dd05a 100644
--- a/drivers/base/firmware_loader/fallback_platform.c
+++ b/drivers/base/firmware_loader/fallback_platform.c
@@ -25,7 +25,10 @@ int firmware_fallback_platform(struct fw_priv *fw_priv, u32 opt_flags)
  	if (rc)
  		return rc; /* rc == -ENOENT when the fw was not found */
- fw_priv->data = vmalloc(size);
+	if (fw_priv->data && size > fw_priv->allocated_size)
+		return -ENOMEM;
+	if (!fw_priv->data)
+		fw_priv->data = vmalloc(size);
  	if (!fw_priv->data)
  		return -ENOMEM;




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