2021-03-10 08:34:05

by Lv Yunlong

Subject: [PATCH] firmware/efi: Fix a use after bug in efi_mem_reserve_persistent

In the for loop in efi_mem_reserve_persistent(), prsv = rsv->next
use the unmapped rsv. Use the unmapped pages will cause segment
fault.

Fixes: 18df7577adae6 ("efi/memreserve: deal with memreserve entries in unmapped memory")
Signed-off-by: Lv Yunlong <[email protected]>
---
drivers/firmware/efi/efi.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index df3f9bcab581..4b7ee3fa9224 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -927,7 +927,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
}

/* first try to find a slot in an existing linked list entry */
- for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
+ for (prsv = efi_memreserve_root->next; prsv; ) {
rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
if (index < rsv->size) {
@@ -937,6 +937,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
memunmap(rsv);
return efi_mem_reserve_iomem(addr, size);
}
+ prsv = rsv->next;
memunmap(rsv);
}

--
2.25.1

2021-03-18 18:20:19

by Ard Biesheuvel

Subject: Re: [PATCH] firmware/efi: Fix a use after bug in efi_mem_reserve_persistent

On Wed, 10 Mar 2021 at 09:37, Lv Yunlong <[email protected]> wrote:
>
> In the for loop in efi_mem_reserve_persistent(), prsv = rsv->next
> use the unmapped rsv. Use the unmapped pages will cause segment
> fault.
>
> Fixes: 18df7577adae6 ("efi/memreserve: deal with memreserve entries in unmapped memory")
> Signed-off-by: Lv Yunlong <[email protected]>

Queued as a fix, thanks.

> ---
> drivers/firmware/efi/efi.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index df3f9bcab581..4b7ee3fa9224 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -927,7 +927,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
> }
>
> /* first try to find a slot in an existing linked list entry */
> - for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
> + for (prsv = efi_memreserve_root->next; prsv; ) {
> rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
> index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
> if (index < rsv->size) {
> @@ -937,6 +937,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
> memunmap(rsv);
> return efi_mem_reserve_iomem(addr, size);
> }
> + prsv = rsv->next;
> memunmap(rsv);
> }
>
> --
> 2.25.1
>
>