From: Lai Jiangshan <laijs@linux.alibaba.com>
To: linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Jann Horn <jannh@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: [PATCH V2 4/4] x86/entry: don't copy to tmp in fixup_bad_iret
Date: Fri, 29 May 2020 08:26:17 +0000 [thread overview]
Message-ID: <20200529082618.1697-5-laijs@linux.alibaba.com> (raw)
In-Reply-To: <20200529082618.1697-1-laijs@linux.alibaba.com>
It is safe to do memcpy() in fixup_bad_iret() now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/kernel/traps.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9d16672865f8..1a0253a80a4c 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -660,17 +660,23 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
* (rather than just below the IRET frame) and we want to
* pretend that the exception came from the IRET target.
*/
- struct bad_iret_stack tmp, *new_stack =
+ struct bad_iret_stack *new_stack =
(struct bad_iret_stack *)__this_cpu_read(cpu_current_top_of_stack) - 1;
- /* Copy the IRET target to the temporary storage. */
- memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8);
+ /*
+ * Both the IRET frame and the saved pt_regs must be on the
+ * entry stacks since iret to user is only issued on the
+ * entry stacks. So they don't overlap with kernel stack and
+ * memcpy() is safe to copy them.
+ */
+ BUG_ON(((unsigned long)s - (unsigned long)new_stack) < PAGE_SIZE ||
+ ((unsigned long)new_stack - (unsigned long)s) < PAGE_SIZE);
- /* Copy the remainder of the stack from the current stack. */
- memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip));
+ /* Copy the IRET target to the new stack. */
+ memcpy(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
- /* Update the entry stack */
- memcpy(new_stack, &tmp, sizeof(tmp));
+ /* Copy the remainder of the stack from the current stack. */
+ memcpy(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
BUG_ON(!user_mode(&new_stack->regs));
return new_stack;
--
2.20.1
next prev parent reply other threads:[~2020-05-29 8:26 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 7:31 [PATCH 0/5] x86/entry: simply stack switching when exception on userspace Lai Jiangshan
2020-05-27 7:31 ` [PATCH 1/5] x86/entry: introduce macro idtentry_swapgs_and_switch_to_kernel_stack Lai Jiangshan
2020-05-28 19:12 ` Thomas Gleixner
2020-05-29 8:26 ` [PATCH V2 0/4] x86/entry: simply stack switching when exception on userspace Lai Jiangshan
2020-05-29 8:26 ` [PATCH V2 1/4] x86/entry: avoid calling into sync_regs() when entering from userspace Lai Jiangshan
2020-05-29 8:26 ` [PATCH V2 2/4] x86/entry: directly switch to kernel stack when .Lerror_bad_iret Lai Jiangshan
2020-05-29 8:26 ` [PATCH V2 3/4] x86/entry: remove unused sync_regs() Lai Jiangshan
2020-05-29 8:26 ` Lai Jiangshan [this message]
2020-05-29 18:32 ` [PATCH V2 0/4] x86/entry: simply stack switching when exception on userspace Andy Lutomirski
2020-06-16 1:56 ` Lai Jiangshan
2020-06-18 13:52 ` Lai Jiangshan
2020-06-18 14:10 ` Thomas Gleixner
2020-06-27 21:03 ` Andy Lutomirski
[not found] ` <20200817062355.2884-1-jiangshanlai@gmail.com>
2020-08-17 5:31 ` [PATCH V3 0/3] " Lai Jiangshan
2020-09-10 10:12 ` Lai Jiangshan
2020-08-17 6:23 ` [PATCH V3 1/3] x86/entry: avoid calling into sync_regs() when entering from userspace Lai Jiangshan
2020-09-11 21:24 ` Jann Horn
2020-09-15 7:55 ` Lai Jiangshan
2020-08-17 6:23 ` [PATCH V3 2/3] x86/entry: directly switch to kernel stack when .Lerror_bad_iret Lai Jiangshan
2020-08-17 6:23 ` [PATCH V3 3/3] x86/entry: remove unused sync_regs() Lai Jiangshan
2020-05-27 7:31 ` [PATCH 2/5] x86/entry: avoid calling into sync_regs() when entering from userspace Lai Jiangshan
2020-05-27 7:31 ` [PATCH 3/5] x86/entry: directly switch to kernel stack when .Lerror_bad_iret Lai Jiangshan
2020-05-27 7:31 ` [PATCH 4/5] x86/entry: remove unused sync_regs() Lai Jiangshan
2020-05-27 7:31 ` [PATCH 5/5] x86/entry: don't copy to tmp in fixup_bad_iret Lai Jiangshan
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