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authorSuresh Siddha <suresh.b.siddha@intel.com>2008-08-15 10:13:20 +1000
committerGreg Kroah-Hartman <gregkh@suse.de>2008-08-20 11:05:15 -0700
commitfaf996d6cdc3a8e6205ae5226f667aa7d1f5f6c2 (patch)
treef9c36768cf94c24bb8dc79453295a4b5bf428c4a
parentf8e6fcea9210eb5e2221643336f74ef007aab498 (diff)
crypto: padlock - fix VIA PadLock instruction usage with irq_ts_save/restore()
crypto: padlock - fix VIA PadLock instruction usage with irq_ts_save/restore() [ Upstream commit: e49140120c88eb99db1a9172d9ac224c0f2bbdd2 ] Wolfgang Walter reported this oops on his via C3 using padlock for AES-encryption: ################################################################## BUG: unable to handle kernel NULL pointer dereference at 000001f0 IP: [<c01028c5>] __switch_to+0x30/0x117 *pde = 00000000 Oops: 0002 [#1] PREEMPT Modules linked in: Pid: 2071, comm: sleep Not tainted (2.6.26 #11) EIP: 0060:[<c01028c5>] EFLAGS: 00010002 CPU: 0 EIP is at __switch_to+0x30/0x117 EAX: 00000000 EBX: c0493300 ECX: dc48dd00 EDX: c0493300 ESI: dc48dd00 EDI: c0493530 EBP: c04cff8c ESP: c04cff7c DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068 Process sleep (pid: 2071, ti=c04ce000 task=dc48dd00 task.ti=d2fe6000) Stack: dc48df30 c0493300 00000000 00000000 d2fe7f44 c03b5b43 c04cffc8 00000046 c0131856 0000005a dc472d3c c0493300 c0493470 d983ae00 00002696 00000000 c0239f54 00000000 c04c4000 c04cffd8 c01025fe c04f3740 00049800 c04cffe0 Call Trace: [<c03b5b43>] ? schedule+0x285/0x2ff [<c0131856>] ? pm_qos_requirement+0x3c/0x53 [<c0239f54>] ? acpi_processor_idle+0x0/0x434 [<c01025fe>] ? cpu_idle+0x73/0x7f [<c03a4dcd>] ? rest_init+0x61/0x63 ======================= Wolfgang also found out that adding kernel_fpu_begin() and kernel_fpu_end() around the padlock instructions fix the oops. Suresh wrote: These padlock instructions though don't use/touch SSE registers, but it behaves similar to other SSE instructions. For example, it might cause DNA faults when cr0.ts is set. While this is a spurious DNA trap, it might cause oops with the recent fpu code changes. This is the code sequence that is probably causing this problem: a) new app is getting exec'd and it is somewhere in between start_thread() and flush_old_exec() in the load_xyz_binary() b) At pont "a", task's fpu state (like TS_USEDFPU, used_math() etc) is cleared. c) Now we get an interrupt/softirq which starts using these encrypt/decrypt routines in the network stack. This generates a math fault (as cr0.ts is '1') which sets TS_USEDFPU and restores the math that is in the task's xstate. d) Return to exec code path, which does start_thread() which does free_thread_xstate() and sets xstate pointer to NULL while the TS_USEDFPU is still set. e) At the next context switch from the new exec'd task to another task, we have a scenarios where TS_USEDFPU is set but xstate pointer is null. This can cause an oops during unlazy_fpu() in __switch_to() Now: 1) This should happen with or with out pre-emption. Viro also encountered similar problem with out CONFIG_PREEMPT. 2) kernel_fpu_begin() and kernel_fpu_end() will fix this problem, because kernel_fpu_begin() will manually do a clts() and won't run in to the situation of setting TS_USEDFPU in step "c" above. 3) This was working before the fpu changes, because its a spurious math fault which doesn't corrupt any fpu/sse registers and the task's math state was always in an allocated state. With out the recent lazy fpu allocation changes, while we don't see oops, there is a possible race still present in older kernels(for example, while kernel is using kernel_fpu_begin() in some optimized clear/copy page and an interrupt/softirq happens which uses these padlock instructions generating DNA fault). This is the failing scenario that existed even before the lazy fpu allocation changes: 0. CPU's TS flag is set 1. kernel using FPU in some optimized copy routine and while doing kernel_fpu_begin() takes an interrupt just before doing clts() 2. Takes an interrupt and ipsec uses padlock instruction. And we take a DNA fault as TS flag is still set. 3. We handle the DNA fault and set TS_USEDFPU and clear cr0.ts 4. We complete the padlock routine 5. Go back to step-1, which resumes clts() in kernel_fpu_begin(), finishes the optimized copy routine and does kernel_fpu_end(). At this point, we have cr0.ts again set to '1' but the task's TS_USEFPU is stilll set and not cleared. 6. Now kernel resumes its user operation. And at the next context switch, kernel sees it has do a FP save as TS_USEDFPU is still set and then will do a unlazy_fpu() in __switch_to(). unlazy_fpu() will take a DNA fault, as cr0.ts is '1' and now, because we are in __switch_to(), math_state_restore() will get confused and will restore the next task's FP state and will save it in prev tasks's FP state. Remember, in __switch_to() we are already on the stack of the next task but take a DNA fault for the prev task. This causes the fpu leakage. Fix the padlock instruction usage by calling them inside the context of new routines irq_ts_save/restore(), which clear/restore cr0.ts manually in the interrupt context. This will not generate spurious DNA in the context of the interrupt which will fix the oops encountered and the possible FPU leakage issue. Reported-and-bisected-by: Wolfgang Walter <wolfgang.walter@stwm.de> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/char/hw_random/via-rng.c8
-rw-r--r--drivers/crypto/padlock-aes.c28
-rw-r--r--drivers/crypto/padlock-sha.c9
-rw-r--r--include/asm-x86/i387.h32
4 files changed, 76 insertions, 1 deletions
diff --git a/drivers/char/hw_random/via-rng.c b/drivers/char/hw_random/via-rng.c
index f7feae4ebb5e..128202e18fc9 100644
--- a/drivers/char/hw_random/via-rng.c
+++ b/drivers/char/hw_random/via-rng.c
@@ -31,6 +31,7 @@
#include <asm/io.h>
#include <asm/msr.h>
#include <asm/cpufeature.h>
+#include <asm/i387.h>
#define PFX KBUILD_MODNAME ": "
@@ -67,16 +68,23 @@ enum {
* Another possible performance boost may come from simply buffering
* until we have 4 bytes, thus returning a u32 at a time,
* instead of the current u8-at-a-time.
+ *
+ * Padlock instructions can generate a spurious DNA fault, so
+ * we have to call them in the context of irq_ts_save/restore()
*/
static inline u32 xstore(u32 *addr, u32 edx_in)
{
u32 eax_out;
+ int ts_state;
+
+ ts_state = irq_ts_save();
asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
:"=m"(*addr), "=a"(eax_out)
:"D"(addr), "d"(edx_in));
+ irq_ts_restore(ts_state);
return eax_out;
}
diff --git a/drivers/crypto/padlock-aes.c b/drivers/crypto/padlock-aes.c
index bb30eb9b93ef..2a5c2db63663 100644
--- a/drivers/crypto/padlock-aes.c
+++ b/drivers/crypto/padlock-aes.c
@@ -16,6 +16,7 @@
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <asm/byteorder.h>
+#include <asm/i387.h>
#include "padlock.h"
/* Control word. */
@@ -141,6 +142,12 @@ static inline void padlock_reset_key(void)
asm volatile ("pushfl; popfl");
}
+/*
+ * While the padlock instructions don't use FP/SSE registers, they
+ * generate a spurious DNA fault when cr0.ts is '1'. These instructions
+ * should be used only inside the irq_ts_save/restore() context
+ */
+
static inline void padlock_xcrypt(const u8 *input, u8 *output, void *key,
void *control_word)
{
@@ -205,15 +212,23 @@ static inline u8 *padlock_xcrypt_cbc(const u8 *input, u8 *output, void *key,
static void aes_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
struct aes_ctx *ctx = aes_ctx(tfm);
+ int ts_state;
padlock_reset_key();
+
+ ts_state = irq_ts_save();
aes_crypt(in, out, ctx->E, &ctx->cword.encrypt);
+ irq_ts_restore(ts_state);
}
static void aes_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
struct aes_ctx *ctx = aes_ctx(tfm);
+ int ts_state;
padlock_reset_key();
+
+ ts_state = irq_ts_save();
aes_crypt(in, out, ctx->D, &ctx->cword.decrypt);
+ irq_ts_restore(ts_state);
}
static struct crypto_alg aes_alg = {
@@ -244,12 +259,14 @@ static int ecb_aes_encrypt(struct blkcipher_desc *desc,
struct aes_ctx *ctx = blk_aes_ctx(desc->tfm);
struct blkcipher_walk walk;
int err;
+ int ts_state;
padlock_reset_key();
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
+ ts_state = irq_ts_save();
while ((nbytes = walk.nbytes)) {
padlock_xcrypt_ecb(walk.src.virt.addr, walk.dst.virt.addr,
ctx->E, &ctx->cword.encrypt,
@@ -257,6 +274,7 @@ static int ecb_aes_encrypt(struct blkcipher_desc *desc,
nbytes &= AES_BLOCK_SIZE - 1;
err = blkcipher_walk_done(desc, &walk, nbytes);
}
+ irq_ts_restore(ts_state);
return err;
}
@@ -268,12 +286,14 @@ static int ecb_aes_decrypt(struct blkcipher_desc *desc,
struct aes_ctx *ctx = blk_aes_ctx(desc->tfm);
struct blkcipher_walk walk;
int err;
+ int ts_state;
padlock_reset_key();
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
+ ts_state = irq_ts_save();
while ((nbytes = walk.nbytes)) {
padlock_xcrypt_ecb(walk.src.virt.addr, walk.dst.virt.addr,
ctx->D, &ctx->cword.decrypt,
@@ -281,7 +301,7 @@ static int ecb_aes_decrypt(struct blkcipher_desc *desc,
nbytes &= AES_BLOCK_SIZE - 1;
err = blkcipher_walk_done(desc, &walk, nbytes);
}
-
+ irq_ts_restore(ts_state);
return err;
}
@@ -314,12 +334,14 @@ static int cbc_aes_encrypt(struct blkcipher_desc *desc,
struct aes_ctx *ctx = blk_aes_ctx(desc->tfm);
struct blkcipher_walk walk;
int err;
+ int ts_state;
padlock_reset_key();
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
+ ts_state = irq_ts_save();
while ((nbytes = walk.nbytes)) {
u8 *iv = padlock_xcrypt_cbc(walk.src.virt.addr,
walk.dst.virt.addr, ctx->E,
@@ -329,6 +351,7 @@ static int cbc_aes_encrypt(struct blkcipher_desc *desc,
nbytes &= AES_BLOCK_SIZE - 1;
err = blkcipher_walk_done(desc, &walk, nbytes);
}
+ irq_ts_restore(ts_state);
return err;
}
@@ -340,12 +363,14 @@ static int cbc_aes_decrypt(struct blkcipher_desc *desc,
struct aes_ctx *ctx = blk_aes_ctx(desc->tfm);
struct blkcipher_walk walk;
int err;
+ int ts_state;
padlock_reset_key();
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt(desc, &walk);
+ ts_state = irq_ts_save();
while ((nbytes = walk.nbytes)) {
padlock_xcrypt_cbc(walk.src.virt.addr, walk.dst.virt.addr,
ctx->D, walk.iv, &ctx->cword.decrypt,
@@ -354,6 +379,7 @@ static int cbc_aes_decrypt(struct blkcipher_desc *desc,
err = blkcipher_walk_done(desc, &walk, nbytes);
}
+ irq_ts_restore(ts_state);
return err;
}
diff --git a/drivers/crypto/padlock-sha.c b/drivers/crypto/padlock-sha.c
index c666b4e0933e..355f8c6b900b 100644
--- a/drivers/crypto/padlock-sha.c
+++ b/drivers/crypto/padlock-sha.c
@@ -22,6 +22,7 @@
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/scatterlist.h>
+#include <asm/i387.h>
#include "padlock.h"
#define SHA1_DEFAULT_FALLBACK "sha1-generic"
@@ -102,6 +103,7 @@ static void padlock_do_sha1(const char *in, char *out, int count)
* PadLock microcode needs it that big. */
char buf[128+16];
char *result = NEAREST_ALIGNED(buf);
+ int ts_state;
((uint32_t *)result)[0] = SHA1_H0;
((uint32_t *)result)[1] = SHA1_H1;
@@ -109,9 +111,12 @@ static void padlock_do_sha1(const char *in, char *out, int count)
((uint32_t *)result)[3] = SHA1_H3;
((uint32_t *)result)[4] = SHA1_H4;
+ /* prevent taking the spurious DNA fault with padlock. */
+ ts_state = irq_ts_save();
asm volatile (".byte 0xf3,0x0f,0xa6,0xc8" /* rep xsha1 */
: "+S"(in), "+D"(result)
: "c"(count), "a"(0));
+ irq_ts_restore(ts_state);
padlock_output_block((uint32_t *)result, (uint32_t *)out, 5);
}
@@ -123,6 +128,7 @@ static void padlock_do_sha256(const char *in, char *out, int count)
* PadLock microcode needs it that big. */
char buf[128+16];
char *result = NEAREST_ALIGNED(buf);
+ int ts_state;
((uint32_t *)result)[0] = SHA256_H0;
((uint32_t *)result)[1] = SHA256_H1;
@@ -133,9 +139,12 @@ static void padlock_do_sha256(const char *in, char *out, int count)
((uint32_t *)result)[6] = SHA256_H6;
((uint32_t *)result)[7] = SHA256_H7;
+ /* prevent taking the spurious DNA fault with padlock. */
+ ts_state = irq_ts_save();
asm volatile (".byte 0xf3,0x0f,0xa6,0xd0" /* rep xsha256 */
: "+S"(in), "+D"(result)
: "c"(count), "a"(0));
+ irq_ts_restore(ts_state);
padlock_output_block((uint32_t *)result, (uint32_t *)out, 8);
}
diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h
index 37672f79dcc8..4b683af883f1 100644
--- a/include/asm-x86/i387.h
+++ b/include/asm-x86/i387.h
@@ -13,6 +13,7 @@
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/regset.h>
+#include <linux/hardirq.h>
#include <asm/asm.h>
#include <asm/processor.h>
#include <asm/sigcontext.h>
@@ -290,6 +291,37 @@ static inline void kernel_fpu_end(void)
preempt_enable();
}
+/*
+ * Some instructions like VIA's padlock instructions generate a spurious
+ * DNA fault but don't modify SSE registers. And these instructions
+ * get used from interrupt context aswell. To prevent these kernel instructions
+ * in interrupt context interact wrongly with other user/kernel fpu usage, we
+ * should use them only in the context of irq_ts_save/restore()
+ */
+static inline int irq_ts_save(void)
+{
+ /*
+ * If we are in process context, we are ok to take a spurious DNA fault.
+ * Otherwise, doing clts() in process context require pre-emption to
+ * be disabled or some heavy lifting like kernel_fpu_begin()
+ */
+ if (!in_interrupt())
+ return 0;
+
+ if (read_cr0() & X86_CR0_TS) {
+ clts();
+ return 1;
+ }
+
+ return 0;
+}
+
+static inline void irq_ts_restore(int TS_state)
+{
+ if (TS_state)
+ stts();
+}
+
#ifdef CONFIG_X86_64
static inline void save_init_fpu(struct task_struct *tsk)