[PATCH 4.14] efi: random: Properly limit the size of the random seed

[Ben Hutchings <ben@decadent.org.uk>]

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Commit be36f9e7517e ("efi: READ_ONCE rng seed size before munmap")
added a READ_ONCE() and also changed the call to
add_bootloader_randomness() to use the local size variable.  Neither
of these changes was actually needed and this was not backported to
the 4.14 stable branch.

Commit 161a438d730d ("efi: random: reduce seed size to 32 bytes")
reverted the addition of READ_ONCE() and added a limit to the value of
size.  This depends on the earlier commit, because size can now differ
from seed->size, but it was wrongly backported to the 4.14 stable
branch by itself.

Apply the missing change to the add_bootloader_randomness() parameter
(except that here we are still using add_device_randomness()).

Fixes: 700485f70e50 ("efi: random: reduce seed size to 32 bytes")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/firmware/efi/efi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index ed981f5e29ae..cc64869d8420 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -541,7 +541,7 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
 			seed = early_memremap(efi.rng_seed,
 					      sizeof(*seed) + size);
 			if (seed != NULL) {
-				add_device_randomness(seed->bits, seed->size);
+				add_device_randomness(seed->bits, size);
 				early_memunmap(seed, sizeof(*seed) + size);
 				pr_notice("seeding entropy pool\n");
 			} else {

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