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From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 1 Dec 2022 00:28:51 +0100
Subject: efi: random: Properly limit the size of the random seed
Forwarded: https://lore.kernel.org/stable/Y4fq5mGUbcKV8VwM@decadent.org.uk/T/
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 4.19 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 4.19 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: 0513592520ae ("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(-)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -570,7 +570,7 @@ int __init efi_config_parse_tables(void
sizeof(*seed) + size);
if (seed != NULL) {
pr_notice("seeding entropy pool\n");
- add_device_randomness(seed->bits, seed->size);
+ add_device_randomness(seed->bits, size);
early_memunmap(seed, sizeof(*seed) + size);
} else {
pr_err("Could not map UEFI random seed!\n");
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