[PATCH 2/2] x86: fix __user annotations

Jann Horn
2019-03-28T21:23:32Z

Fix __user annotations in various places across the x86 tree:

- cast to wrong pointer type in __user_atomic_cmpxchg_inatomic()
- generic_load_microcode() deals with a pointer that can be either a
kernel pointer or a user pointer; change the code to pass it around as
a __user pointer, and add explicit casts to convert between __user and
__kernel
- save_xstate_epilog() has missing __user in explicit casts
- setup_sigcontext() and x32_setup_rt_frame() rely on the cast performed
by put_user_ex() on its first argument, but sparse requires __force for
casting __user pointers to unsigned long
- xen_hvm_config() has missing __user

This patch removes all sparse warnings about the asn:1 address space
(__user) in arch/x86/ for my kernel config.

Signed-off-by: Jann Horn <jannh@google.com>
---
This patch requires the previous one, "[PATCH 1/2] kernel.h: use
parentheses around argument in u64_to_user_ptr()", otherwise
xen_hvm_config() breaks. Can we take both together through the x86 tree,
or does the first one have to go through akpm's tree?

arch/x86/include/asm/uaccess.h | 3 +--
arch/x86/include/asm/uaccess_64.h | 2 +-
arch/x86/kernel/cpu/microcode/intel.c | 20 ++++++++++++--------
arch/x86/kernel/fpu/signal.c | 6 +++---
arch/x86/kernel/signal.c | 4 ++--
arch/x86/kvm/x86.c | 8 ++++----
arch/x86/lib/usercopy_64.c | 4 +++-
7 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1954dd5552a2..a21f2a2f17bf 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -585,7 +585,6 @@ extern void __cmpxchg_wrong_size(void)
#define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size) \
({ \
int __ret = 0; \
- __typeof__(ptr) __uval = (uval); \
__typeof__(*(ptr)) __old = (old); \
__typeof__(*(ptr)) __new = (new); \
__uaccess_begin_nospec(); \
@@ -661,7 +660,7 @@ extern void __cmpxchg_wrong_size(void)
__cmpxchg_wrong_size(); \
} \
__uaccess_end(); \
- *__uval = __old; \
+ *(uval) = __old; \
__ret; \
})

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index a9d637bc301d..cbca2cb28939 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -208,7 +208,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
}

unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len);
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len);

unsigned long
mcsafe_handle_tail(char *to, char *from, unsigned len);
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 16936a24795c..e8ef65c275c7 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -861,11 +861,13 @@ static enum ucode_state apply_microcode_intel(int cpu)
return ret;
}

-static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
- int (*get_ucode_data)(void *, const void *, size_t))
+static enum ucode_state generic_load_microcode(int cpu,
+ const void __user *data, size_t size,
+ int (*get_ucode_data)(void *, const void __user *, size_t))
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
- u8 *ucode_ptr = data, *new_mc = NULL, *mc = NULL;
+ const u8 __user *ucode_ptr = data;
+ u8 *new_mc = NULL, *mc = NULL;
int new_rev = uci->cpu_sig.rev;
unsigned int leftover = size;
unsigned int curr_mc_size = 0, new_mc_size = 0;
@@ -945,9 +947,10 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
return ret;
}

-static int get_ucode_fw(void *to, const void *from, size_t n)
+static int get_ucode_fw(void *to, const void __user *from, size_t n)
{
- memcpy(to, from, n);
+ /* cast paired with request_microcode_fw() */
+ memcpy(to, (const void __force *)from, n);
return 0;
}

@@ -993,7 +996,8 @@ static enum ucode_state request_microcode_fw(int cpu, struct device *device,
return UCODE_NFOUND;
}

- ret = generic_load_microcode(cpu, (void *)firmware->data,
+ /* cast paired with get_ucode_fw() */
+ ret = generic_load_microcode(cpu, (void __force __user *)firmware->data,
firmware->size, &get_ucode_fw);

release_firmware(firmware);
@@ -1001,7 +1005,7 @@ static enum ucode_state request_microcode_fw(int cpu, struct device *device,
return ret;
}

-static int get_ucode_user(void *to, const void *from, size_t n)
+static int get_ucode_user(void *to, const void __user *from, size_t n)
{
return copy_from_user(to, from, n);
}
@@ -1012,7 +1016,7 @@ request_microcode_user(int cpu, const void __user *buf, size_t size)
if (is_blacklisted(cpu))
return UCODE_NFOUND;

- return generic_load_microcode(cpu, (void *)buf, size, &get_ucode_user);
+ return generic_load_microcode(cpu, buf, size, &get_ucode_user);
}

static struct microcode_ops microcode_intel_ops = {
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index f6a1d299627c..55b80de13ea5 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -92,13 +92,13 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
return err;

err |= __put_user(FP_XSTATE_MAGIC2,
- (__u32 *)(buf + fpu_user_xstate_size));
+ (__u32 __user *)(buf + fpu_user_xstate_size));

/*
* Read the xfeatures which we copied (directly from the cpu or
* from the state in task struct) to the user buffers.
*/
- err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
+ err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);

/*
* For legacy compatible, we always set FP/SSE bits in the bit
@@ -113,7 +113,7 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
*/
xfeatures |= XFEATURE_MASK_FPSSE;

- err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
+ err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);

return err;
}
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 08dfd4c1a4f9..e13cd972f9af 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -206,7 +206,7 @@ int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
put_user_ex(regs->ss, &sc->ss);
#endif /* CONFIG_X86_32 */

- put_user_ex(fpstate, &sc->fpstate);
+ put_user_ex((unsigned long __force)fpstate, &sc->fpstate);

/* non-iBCS2 extensions.. */
put_user_ex(mask, &sc->oldmask);
@@ -569,7 +569,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
restorer = NULL;
err |= -EFAULT;
}
- put_user_ex(restorer, &frame->pretcode);
+ put_user_ex((unsigned long __force)restorer, &frame->pretcode);
} put_user_catch(err);

err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 65e4559eef2f..ca087debefbf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2317,11 +2317,11 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
static int xen_hvm_config(struct kvm_vcpu *vcpu, u64 data)
{
struct kvm *kvm = vcpu->kvm;
+ struct kvm_xen_hvm_config *cfg = &kvm->arch.xen_hvm_config;
int lm = is_long_mode(vcpu);
- u8 *blob_addr = lm ? (u8 *)(long)kvm->arch.xen_hvm_config.blob_addr_64
- : (u8 *)(long)kvm->arch.xen_hvm_config.blob_addr_32;
- u8 blob_size = lm ? kvm->arch.xen_hvm_config.blob_size_64
- : kvm->arch.xen_hvm_config.blob_size_32;
+ u8 __user *blob_addr =
+ u64_to_user_ptr(lm ? cfg->blob_addr_64 : cfg->blob_addr_32);
+ u8 blob_size = lm ? cfg->blob_size_64 : cfg->blob_size_32;
u32 page_num = data & ~PAGE_MASK;
u64 page_addr = data & PAGE_MASK;
u8 *page;
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index ee42bb0cbeb3..cd8a1802adde 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -58,9 +58,11 @@ EXPORT_SYMBOL(clear_user);
* Try to copy last bytes and clear the rest if needed.
* Since protection fault in copy_from/to_user is not a normal situation,
* it is not necessary to optimize tail handling.
+ * We don't know which side of the copy is in userspace; we treat both sides as
+ * user pointers.
*/
__visible unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len)
+copy_user_handle_tail(char __user *to, char __user *from, unsigned len)
{
for (; len; --len, to++) {
char c;
--
2.21.0.392.gf8f6787159e-goog