* [PATCH] x86_64: fixup TASK_SIZE_MAX comment
@ 2020-03-05 18:17 Alexey Dobriyan
2020-03-06 18:09 ` Andy Lutomirski
2021-02-05 9:43 ` [tip: x86/cleanups] x86/asm: Fixup " tip-bot2 for Alexey Dobriyan
0 siblings, 2 replies; 3+ messages in thread
From: Alexey Dobriyan @ 2020-03-05 18:17 UTC (permalink / raw)
To: tglx, mingo, bp, hpa; +Cc: x86, linux-kernel
Comment says "by preventing anything executable" which is not true.
Even PROT_NONE mapping can't be installed at (1<<47 - 4096).
mmap(0x7ffffffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM
I wonder if CPUs with wider address space carried the bugs...
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
arch/x86/include/asm/processor.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -887,7 +887,7 @@ static inline void spin_lock_prefetch(const void *x)
* On Intel CPUs, if a SYSCALL instruction is at the highest canonical
* address, then that syscall will enter the kernel with a
* non-canonical return address, and SYSRET will explode dangerously.
- * We avoid this particular problem by preventing anything executable
+ * We avoid this particular problem by preventing anything
* from being mapped at the maximum canonical address.
*
* On AMD CPUs in the Ryzen family, there's a nasty bug in which the
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86_64: fixup TASK_SIZE_MAX comment
2020-03-05 18:17 [PATCH] x86_64: fixup TASK_SIZE_MAX comment Alexey Dobriyan
@ 2020-03-06 18:09 ` Andy Lutomirski
2021-02-05 9:43 ` [tip: x86/cleanups] x86/asm: Fixup " tip-bot2 for Alexey Dobriyan
1 sibling, 0 replies; 3+ messages in thread
From: Andy Lutomirski @ 2020-03-06 18:09 UTC (permalink / raw)
To: Alexey Dobriyan
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, H. Peter Anvin,
X86 ML, LKML
On Thu, Mar 5, 2020 at 10:17 AM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> Comment says "by preventing anything executable" which is not true.
> Even PROT_NONE mapping can't be installed at (1<<47 - 4096).
>
> mmap(0x7ffffffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM
Reviewed-by: Andy Lutomirski <luto@kernel.org>
>
> I wonder if CPUs with wider address space carried the bugs...
I believe they do. I won't swear to it.
FWIW, I specifically asked Intel to kindly fix this bug^Wfeature as
part of LA57, and I did not get a helpful response.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip: x86/cleanups] x86/asm: Fixup TASK_SIZE_MAX comment
2020-03-05 18:17 [PATCH] x86_64: fixup TASK_SIZE_MAX comment Alexey Dobriyan
2020-03-06 18:09 ` Andy Lutomirski
@ 2021-02-05 9:43 ` tip-bot2 for Alexey Dobriyan
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Alexey Dobriyan @ 2021-02-05 9:43 UTC (permalink / raw)
To: linux-tip-commits
Cc: Alexey Dobriyan, Borislav Petkov, Andy Lutomirski, x86, linux-kernel
The following commit has been merged into the x86/cleanups branch of tip:
Commit-ID: 4f63b320afdd9af406f4426b0ff1a2cdb23e5b8d
Gitweb: https://git.kernel.org/tip/4f63b320afdd9af406f4426b0ff1a2cdb23e5b8d
Author: Alexey Dobriyan <adobriyan@gmail.com>
AuthorDate: Thu, 05 Mar 2020 21:17:19 +03:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 05 Feb 2021 10:37:39 +01:00
x86/asm: Fixup TASK_SIZE_MAX comment
Comment says "by preventing anything executable" which is not true. Even
PROT_NONE mapping can't be installed at (1<<47 - 4096).
mmap(0x7ffffffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM
[ bp: Fixup to the moved location in page_64_types.h. ]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200305181719.GA5490@avx2
---
arch/x86/include/asm/page_64_types.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 645bd1d..64297ea 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -66,7 +66,7 @@
* On Intel CPUs, if a SYSCALL instruction is at the highest canonical
* address, then that syscall will enter the kernel with a
* non-canonical return address, and SYSRET will explode dangerously.
- * We avoid this particular problem by preventing anything executable
+ * We avoid this particular problem by preventing anything
* from being mapped at the maximum canonical address.
*
* On AMD CPUs in the Ryzen family, there's a nasty bug in which the
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2020-03-06 18:09 ` Andy Lutomirski
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