ARM: 8813/1: Make aligned 2-byte getuser()/putuser() atomic on ARMv6+
[ Upstream commit 344eb5539a
]
getuser() and putuser() (and there underscored variants) use two
strb[t]/ldrb[t] instructions when they are asked to get/put 16-bits.
This means that the read/write is not atomic even when performed to a
16-bit-aligned address.
This leads to problems with vhost: vhost uses __getuser() to read the
vring's 16-bit avail.index field, and if it happens to observe a partial
update of the index, wrong descriptors will be used which will lead to a
breakdown of the virtio communication. A similar problem exists for
__putuser() which is used to write to the vring's used.index field.
The reason these functions use strb[t]/ldrb[t] is because strht/ldrht
instructions did not exist until ARMv6T2/ARMv7. So we should be easily
able to fix this on ARMv7. Also, since all ARMv6 processors also don't
actually use the unprivileged instructions anymore for uaccess (since
CONFIG_CPU_USE_DOMAINS is not used) we can easily fix them too.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
committed by
Greg Kroah-Hartman
parent
42abc22c7b
commit
d72b077503
@ -387,6 +387,13 @@ do { \
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#define __get_user_asm_byte(x, addr, err) \
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#define __get_user_asm_byte(x, addr, err) \
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__get_user_asm(x, addr, err, ldrb)
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__get_user_asm(x, addr, err, ldrb)
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#if __LINUX_ARM_ARCH__ >= 6
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#define __get_user_asm_half(x, addr, err) \
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__get_user_asm(x, addr, err, ldrh)
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#else
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#ifndef __ARMEB__
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#ifndef __ARMEB__
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#define __get_user_asm_half(x, __gu_addr, err) \
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#define __get_user_asm_half(x, __gu_addr, err) \
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({ \
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({ \
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@ -405,6 +412,8 @@ do { \
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})
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})
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#endif
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#endif
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#endif /* __LINUX_ARM_ARCH__ >= 6 */
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#define __get_user_asm_word(x, addr, err) \
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#define __get_user_asm_word(x, addr, err) \
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__get_user_asm(x, addr, err, ldr)
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__get_user_asm(x, addr, err, ldr)
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#endif
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#endif
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@ -480,6 +489,13 @@ do { \
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#define __put_user_asm_byte(x, __pu_addr, err) \
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#define __put_user_asm_byte(x, __pu_addr, err) \
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__put_user_asm(x, __pu_addr, err, strb)
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__put_user_asm(x, __pu_addr, err, strb)
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#if __LINUX_ARM_ARCH__ >= 6
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#define __put_user_asm_half(x, __pu_addr, err) \
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__put_user_asm(x, __pu_addr, err, strh)
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#else
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#ifndef __ARMEB__
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#ifndef __ARMEB__
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#define __put_user_asm_half(x, __pu_addr, err) \
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#define __put_user_asm_half(x, __pu_addr, err) \
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({ \
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({ \
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@ -496,6 +512,8 @@ do { \
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})
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})
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#endif
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#endif
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#endif /* __LINUX_ARM_ARCH__ >= 6 */
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#define __put_user_asm_word(x, __pu_addr, err) \
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#define __put_user_asm_word(x, __pu_addr, err) \
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__put_user_asm(x, __pu_addr, err, str)
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__put_user_asm(x, __pu_addr, err, str)
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@ -42,6 +42,12 @@ _ASM_NOKPROBE(__get_user_1)
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ENTRY(__get_user_2)
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ENTRY(__get_user_2)
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check_uaccess r0, 2, r1, r2, __get_user_bad
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check_uaccess r0, 2, r1, r2, __get_user_bad
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#if __LINUX_ARM_ARCH__ >= 6
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2: TUSER(ldrh) r2, [r0]
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#else
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#ifdef CONFIG_CPU_USE_DOMAINS
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#ifdef CONFIG_CPU_USE_DOMAINS
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rb .req ip
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rb .req ip
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2: ldrbt r2, [r0], #1
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2: ldrbt r2, [r0], #1
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@ -56,6 +62,9 @@ rb .req r0
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#else
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#else
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orr r2, rb, r2, lsl #8
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orr r2, rb, r2, lsl #8
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#endif
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#endif
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#endif /* __LINUX_ARM_ARCH__ >= 6 */
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mov r0, #0
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mov r0, #0
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ret lr
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ret lr
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ENDPROC(__get_user_2)
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ENDPROC(__get_user_2)
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@ -145,7 +154,9 @@ _ASM_NOKPROBE(__get_user_bad8)
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.pushsection __ex_table, "a"
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.pushsection __ex_table, "a"
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.long 1b, __get_user_bad
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.long 1b, __get_user_bad
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.long 2b, __get_user_bad
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.long 2b, __get_user_bad
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#if __LINUX_ARM_ARCH__ < 6
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.long 3b, __get_user_bad
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.long 3b, __get_user_bad
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#endif
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.long 4b, __get_user_bad
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.long 4b, __get_user_bad
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.long 5b, __get_user_bad8
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.long 5b, __get_user_bad8
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.long 6b, __get_user_bad8
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.long 6b, __get_user_bad8
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@ -41,16 +41,13 @@ ENDPROC(__put_user_1)
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ENTRY(__put_user_2)
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ENTRY(__put_user_2)
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check_uaccess r0, 2, r1, ip, __put_user_bad
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check_uaccess r0, 2, r1, ip, __put_user_bad
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mov ip, r2, lsr #8
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#if __LINUX_ARM_ARCH__ >= 6
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#ifdef CONFIG_THUMB2_KERNEL
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#ifndef __ARMEB__
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2: TUSER(strh) r2, [r0]
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2: TUSER(strb) r2, [r0]
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3: TUSER(strb) ip, [r0, #1]
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#else
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#else
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2: TUSER(strb) ip, [r0]
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3: TUSER(strb) r2, [r0, #1]
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mov ip, r2, lsr #8
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#endif
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#else /* !CONFIG_THUMB2_KERNEL */
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#ifndef __ARMEB__
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#ifndef __ARMEB__
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2: TUSER(strb) r2, [r0], #1
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2: TUSER(strb) r2, [r0], #1
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3: TUSER(strb) ip, [r0]
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3: TUSER(strb) ip, [r0]
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@ -58,7 +55,8 @@ ENTRY(__put_user_2)
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2: TUSER(strb) ip, [r0], #1
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2: TUSER(strb) ip, [r0], #1
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3: TUSER(strb) r2, [r0]
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3: TUSER(strb) r2, [r0]
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#endif
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#endif
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#endif /* CONFIG_THUMB2_KERNEL */
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#endif /* __LINUX_ARM_ARCH__ >= 6 */
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mov r0, #0
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mov r0, #0
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ret lr
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ret lr
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ENDPROC(__put_user_2)
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ENDPROC(__put_user_2)
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@ -91,7 +89,9 @@ ENDPROC(__put_user_bad)
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.pushsection __ex_table, "a"
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.pushsection __ex_table, "a"
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.long 1b, __put_user_bad
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.long 1b, __put_user_bad
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.long 2b, __put_user_bad
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.long 2b, __put_user_bad
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#if __LINUX_ARM_ARCH__ < 6
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.long 3b, __put_user_bad
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.long 3b, __put_user_bad
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#endif
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.long 4b, __put_user_bad
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.long 4b, __put_user_bad
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.long 5b, __put_user_bad
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.long 5b, __put_user_bad
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.long 6b, __put_user_bad
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.long 6b, __put_user_bad
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