[LTP] ❌ FAIL: Test report for kernel 5.4.0-rc2-d6c2c23.cki (stable-next)

Wed Oct 16 06:29:33 CEST 2019

On Tue, Oct 15, 2019 at 05:14:53PM +0100, Will Deacon wrote:
> On Tue, Oct 15, 2019 at 04:26:51PM +0100, Catalin Marinas wrote:
> > On Mon, Oct 14, 2019 at 10:33:32PM +0100, Will Deacon wrote:
> > > On Mon, Oct 14, 2019 at 05:26:51PM +0100, Catalin Marinas wrote:
> > > > The options I see:
> > > > 
> > > > 1. Revert commit 057d3389108e and try again to document that the memory
> > > >    syscalls do not support tagged pointers
> > > > 
> > > > 2. Change untagged_addr() to only 0-extend from bit 55 or leave the
> > > >    tag unchanged if bit 55 is 1. We could mask out the tag (0 rather
> > > >    than sign-extend) but if we had an mlock test passing ULONG_MASK,
> > > >    then we get -ENOMEM instead of -EINVAL
> > > > 
> > > > 3. Make untagged_addr() depend on the TIF_TAGGED_ADDR bit and we only
> > > >    break the ABI for applications opting in to this new ABI. We did look
> > > >    at this but the ptrace(PEEK/POKE_DATA) needs a bit more thinking on
> > > >    whether we check the ptrace'd process or the debugger flags
> > > > 
> > > > 4. Leave things as they are, consider the address space 56-bit and
> > > >    change the test to not use LONG_MAX on arm64. This needs to be passed
> > > >    by the sparc guys since they probably have a similar issue
> > > 
> > > I'm in favour of (2) or (4) as long as there's also an update to the docs.
> > 
> > With (4) we'd start differing from other architectures supported by
> > Linux. This works if we consider the test to be broken. However, reading
> > the mlock man page:
> > 
> >        EINVAL The result of the addition addr+len was less than addr
> >        (e.g., the addition may have resulted in an overflow).
> > 
> >        ENOMEM Some of the specified address range does not correspond to
> >        mapped pages in the address space of the process.
> > 
> > There is no mention of EINVAL outside the TASK_SIZE, seems to fall more
> > within the ENOMEM description above.
> 
> Sorry, I was being too vague in my wording. What I was trying to say is I'm
> ok with (2) or (4), but either way we need to update our ABI documentation
> under Documentation/arm64/.

Having looked at making that change, I actually think the text is ok as-is
if we go with option (2). We only make guarantees about "valid tagged
pointer", which are defined to "reference an address in the user process
address space" and therefore must have bit 55 == 0.

Untested patch below.

Will

--->8

>From 517d979e84191ae9997c9513a88a5b798af6912f Mon Sep 17 00:00:00 2001
From: Will Deacon <will@kernel.org>
Date: Tue, 15 Oct 2019 21:04:18 -0700
Subject: [PATCH] arm64: tags: Preserve tags for addresses translated via TTBR1

Sign-extending TTBR1 addresses when converting to an untagged address
breaks the documented POSIX semantics for mlock() in some obscure error
cases where we end up returning -EINVAL instead of -ENOMEM as a direct
result of rewriting the upper address bits.

Rework the untagged_addr() macro to preserve the upper address bits for
TTBR1 addresses and only clear the tag bits for user addresses. This
matches the behaviour of the 'clear_address_tag' assembly macro, so
rename that and align the implementations at the same time so that they
use the same instruction sequences for the tag manipulation.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/stable/20191014162651.GF19200@arrakis.emea.arm.com/
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/asm-uaccess.h |  7 +++----
 arch/arm64/include/asm/memory.h      | 10 ++++++++--
 arch/arm64/kernel/entry.S            |  4 ++--
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index f74909ba29bd..5bf963830b17 100644
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -78,10 +78,9 @@ alternative_else_nop_endif
 /*
  * Remove the address tag from a virtual address, if present.
  */
-	.macro	clear_address_tag, dst, addr
-	tst	\addr, #(1 << 55)
-	bic	\dst, \addr, #(0xff << 56)
-	csel	\dst, \dst, \addr, eq
+	.macro	untagged_addr, dst, addr
+	sbfx	\dst, \addr, #0, #56
+	and	\dst, \dst, \addr
 	.endm
 
 #endif
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b61b50bf68b1..c23c47360664 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -215,12 +215,18 @@ static inline unsigned long kaslr_offset(void)
  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
  * pass on to access_ok(), for instance.
  */
-#define untagged_addr(addr)	\
+#define __untagged_addr(addr)	\
 	((__force __typeof__(addr))sign_extend64((__force u64)(addr), 55))
 
+#define untagged_addr(addr)	({					\
+	u64 __addr = (__force u64)addr;					\
+	__addr &= __untagged_addr(__addr);				\
+	(__force __typeof__(addr))__addr;				\
+})
+
 #ifdef CONFIG_KASAN_SW_TAGS
 #define __tag_shifted(tag)	((u64)(tag) << 56)
-#define __tag_reset(addr)	untagged_addr(addr)
+#define __tag_reset(addr)	__untagged_addr(addr)
 #define __tag_get(addr)		(__u8)((u64)(addr) >> 56)
 #else
 #define __tag_shifted(tag)	0UL
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e304fe04b098..9ae336cc5833 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -604,7 +604,7 @@ el1_da:
 	 */
 	mrs	x3, far_el1
 	inherit_daif	pstate=x23, tmp=x2
-	clear_address_tag x0, x3
+	untagged_addr	x0, x3
 	mov	x2, sp				// struct pt_regs
 	bl	do_mem_abort
 
@@ -808,7 +808,7 @@ el0_da:
 	mrs	x26, far_el1
 	ct_user_exit_irqoff
 	enable_daif
-	clear_address_tag x0, x26
+	untagged_addr	x0, x26
 	mov	x1, x25
 	mov	x2, sp
 	bl	do_mem_abort
-- 
2.23.0.700.g56cf767bdb-goog

