From: Ira Weiny <[email protected]>
kmap is inefficient and is being replaced by kmap_local_page(), if
possible.
That said, there is no readily apparent reason why initp_page needs to
be allocated and kmap'ed() except that 'sigstruct' needs to be page
aligned and 'token' 512 byte aligned.
Rather than change this kmap() to kmap_local_page() use kmalloc()
instead because kmalloc() can gives this alignment when allocating
PAGE_SIZE bytes.
Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
to get a page aligned kernel address.
In addition add a comment to document the alignment requirements so that
others don't attempt to 'fix' this again.
Cc: Sean Christopherson <[email protected]>
Cc: Jethro Beekman <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: Dave Hansen <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
---
Changes from v5[5]:
From Boris
Clean up commit msg and comment
Changes from v4[4]:
Add Ack and Reviews
Send to the correct maintainers
Changes from v3[3]:
Remove BUILD_BUG_ONs
Changes from v2[2]:
When allocating a power of 2 size kmalloc() now guarantees the
alignment of the respective size. So go back to using kmalloc() but
with a PAGE_SIZE allocation to get the alignment. This also follows
the pattern in sgx_ioc_enclave_create()
Changes from v1[1]:
Use page_address() instead of kcmalloc() to ensure sigstruct is
page aligned
Use BUILD_BUG_ON to ensure token and sigstruct don't collide.
[1] https://lore.kernel.org/lkml/[email protected]/
[2] https://lore.kernel.org/lkml/[email protected]/
[3] https://lore.kernel.org/lkml/[email protected]/#t
[4] https://lore.kernel.org/lkml/[email protected]/
[5] https://lore.kernel.org/lkml/[email protected]/
---
arch/x86/kernel/cpu/sgx/ioctl.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 90a5caf76939..2e10367ea66c 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -604,7 +604,6 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
{
struct sgx_sigstruct *sigstruct;
struct sgx_enclave_init init_arg;
- struct page *initp_page;
void *token;
int ret;
@@ -615,11 +614,15 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
if (copy_from_user(&init_arg, arg, sizeof(init_arg)))
return -EFAULT;
- initp_page = alloc_page(GFP_KERNEL);
- if (!initp_page)
+ /*
+ * 'sigstruct' must be on a page boundary and 'token' on a 512 byte
+ * boundary. kmalloc() will give this alignment when allocating
+ * PAGE_SIZE bytes.
+ */
+ sigstruct = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!sigstruct)
return -ENOMEM;
- sigstruct = kmap(initp_page);
token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2);
memset(token, 0, SGX_LAUNCH_TOKEN_SIZE);
@@ -645,8 +648,7 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
ret = sgx_encl_init(encl, sigstruct, token);
out:
- kunmap(initp_page);
- __free_page(initp_page);
+ kfree(sigstruct);
return ret;
}
--
2.28.0.rc0.12.gb6a658bd00c9
The following commit has been merged into the x86/sgx branch of tip:
Commit-ID: 633b0616cfe085679471a4c0fae02e8c3a1a9866
Gitweb: https://git.kernel.org/tip/633b0616cfe085679471a4c0fae02e8c3a1a9866
Author: Ira Weiny <[email protected]>
AuthorDate: Wed, 24 Mar 2021 11:22:46 -07:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Thu, 25 Mar 2021 09:50:32 +01:00
x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init()
kmap() is inefficient and is being replaced by kmap_local_page(), if
possible. There is no readily apparent reason why initp_page needs to be
allocated and kmap'ed() except that 'sigstruct' needs to be page-aligned
and 'token' 512 byte-aligned.
Rather than change it to kmap_local_page(), use kmalloc() instead
because kmalloc() can give this alignment when allocating PAGE_SIZE
bytes.
Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
to get a page aligned kernel address.
In addition, add a comment to document the alignment requirements so that
others don't attempt to 'fix' this again.
[ bp: Massage commit message. ]
Signed-off-by: Ira Weiny <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/kernel/cpu/sgx/ioctl.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 90a5caf..2e10367 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -604,7 +604,6 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
{
struct sgx_sigstruct *sigstruct;
struct sgx_enclave_init init_arg;
- struct page *initp_page;
void *token;
int ret;
@@ -615,11 +614,15 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
if (copy_from_user(&init_arg, arg, sizeof(init_arg)))
return -EFAULT;
- initp_page = alloc_page(GFP_KERNEL);
- if (!initp_page)
+ /*
+ * 'sigstruct' must be on a page boundary and 'token' on a 512 byte
+ * boundary. kmalloc() will give this alignment when allocating
+ * PAGE_SIZE bytes.
+ */
+ sigstruct = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!sigstruct)
return -ENOMEM;
- sigstruct = kmap(initp_page);
token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2);
memset(token, 0, SGX_LAUNCH_TOKEN_SIZE);
@@ -645,8 +648,7 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
ret = sgx_encl_init(encl, sigstruct, token);
out:
- kunmap(initp_page);
- __free_page(initp_page);
+ kfree(sigstruct);
return ret;
}
On Wed, Mar 24, 2021 at 11:22:46AM -0700, [email protected] wrote:
> From: Ira Weiny <[email protected]>
>
> kmap is inefficient and is being replaced by kmap_local_page(), if
> possible.
Nit: just saying that something is inefficient is not enough. Always
should have something to back it up.
> That said, there is no readily apparent reason why initp_page needs to
> be allocated and kmap'ed() except that 'sigstruct' needs to be page
> aligned and 'token' 512 byte aligned.
>
> Rather than change this kmap() to kmap_local_page() use kmalloc()
> instead because kmalloc() can gives this alignment when allocating
> PAGE_SIZE bytes.
>
> Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
> to get a page aligned kernel address.
>
> In addition add a comment to document the alignment requirements so that
> others don't attempt to 'fix' this again.
I'm a bit confused based on this commit message. Why is kmap_local_page()
better, and why kmalloc() is the ultimate choice of all three options?
>
> Cc: Sean Christopherson <[email protected]>
> Cc: Jethro Beekman <[email protected]>
> Cc: Jarkko Sakkinen <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Signed-off-by: Ira Weiny <[email protected]>
/Jarkko