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884b426917
linux/arch/mips/cavium-octeon/octeon-memcpy.S
James Cowgill 884b426917 MIPS: OCTEON: Fix copy_from_user fault handling for large buffers 
If copy_from_user is called with a large buffer (>= 128 bytes) and the
userspace buffer refers partially to unreadable memory, then it is
possible for Octeon's copy_from_user to report the wrong number of bytes
have been copied. In the case where the buffer size is an exact multiple
of 128 and the fault occurs in the last 64 bytes, copy_from_user will
report that all the bytes were copied successfully but leave some
garbage in the destination buffer.

The bug is in the main __copy_user_common loop in octeon-memcpy.S where
in the middle of the loop, src and dst are incremented by 128 bytes. The
l_exc_copy fault handler is used after this but that assumes that
"src < THREAD_BUADDR($28)". This is not the case if src has already been
incremented.

Fix by adding an extra fault handler which rewinds the src and dst
pointers 128 bytes before falling though to l_exc_copy.

Thanks to the pwritev test from the strace test suite for originally
highlighting this bug!

Fixes: 5b3b16880f ("MIPS: Add Cavium OCTEON processor support ...")
Signed-off-by: James Cowgill <James.Cowgill@imgtec.com>
Acked-by: David Daney <david.daney@cavium.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14978/
Signed-off-by: James Hogan <james.hogan@imgtec.com>
2017-02-17 11:14:28 +00:00

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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Unified implementation of memcpy, memmove and the __copy_user backend.
*
* Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
* Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
* Copyright (C) 2002 Broadcom, Inc.
* memcpy/copy_user author: Mark Vandevoorde
*
* Mnemonic names for arguments to memcpy/__copy_user
*/
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/export.h>
#include <asm/regdef.h>
#define dst a0
#define src a1
#define len a2
/*
* Spec
*
* memcpy copies len bytes from src to dst and sets v0 to dst.
* It assumes that
* - src and dst don't overlap
* - src is readable
* - dst is writable
* memcpy uses the standard calling convention
*
* __copy_user copies up to len bytes from src to dst and sets a2 (len) to
* the number of uncopied bytes due to an exception caused by a read or write.
* __copy_user assumes that src and dst don't overlap, and that the call is
* implementing one of the following:
* copy_to_user
* - src is readable (no exceptions when reading src)
* copy_from_user
* - dst is writable (no exceptions when writing dst)
* __copy_user uses a non-standard calling convention; see
* arch/mips/include/asm/uaccess.h
*
* When an exception happens on a load, the handler must
# ensure that all of the destination buffer is overwritten to prevent
* leaking information to user mode programs.
*/
/*
* Implementation
*/
/*
* The exception handler for loads requires that:
* 1- AT contain the address of the byte just past the end of the source
* of the copy,
* 2- src_entry <= src < AT, and
* 3- (dst - src) == (dst_entry - src_entry),
* The _entry suffix denotes values when __copy_user was called.
*
* (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
* (2) is met by incrementing src by the number of bytes copied
* (3) is met by not doing loads between a pair of increments of dst and src
*
* The exception handlers for stores adjust len (if necessary) and return.
* These handlers do not need to overwrite any data.
*
* For __rmemcpy and memmove an exception is always a kernel bug, therefore
* they're not protected.
*/
#define EXC(inst_reg,addr,handler) \
9: inst_reg, addr; \
.section __ex_table,"a"; \
PTR 9b, handler; \
.previous
/*
* Only on the 64-bit kernel we can made use of 64-bit registers.
*/
#define LOAD ld
#define LOADL ldl
#define LOADR ldr
#define STOREL sdl
#define STORER sdr
#define STORE sd
#define ADD daddu
#define SUB dsubu
#define SRL dsrl
#define SRA dsra
#define SLL dsll
#define SLLV dsllv
#define SRLV dsrlv
#define NBYTES 8
#define LOG_NBYTES 3
/*
* As we are sharing code base with the mips32 tree (which use the o32 ABI
* register definitions). We need to redefine the register definitions from
* the n64 ABI register naming to the o32 ABI register naming.
*/
#undef t0
#undef t1
#undef t2
#undef t3
#define t0 $8
#define t1 $9
#define t2 $10
#define t3 $11
#define t4 $12
#define t5 $13
#define t6 $14
#define t7 $15
#ifdef CONFIG_CPU_LITTLE_ENDIAN
#define LDFIRST LOADR
#define LDREST LOADL
#define STFIRST STORER
#define STREST STOREL
#define SHIFT_DISCARD SLLV
#else
#define LDFIRST LOADL
#define LDREST LOADR
#define STFIRST STOREL
#define STREST STORER
#define SHIFT_DISCARD SRLV
#endif
#define FIRST(unit) ((unit)*NBYTES)
#define REST(unit) (FIRST(unit)+NBYTES-1)
#define UNIT(unit) FIRST(unit)
#define ADDRMASK (NBYTES-1)
.text
.set noreorder
.set noat
/*
* t7 is used as a flag to note inatomic mode.
*/
LEAF(__copy_user_inatomic)
EXPORT_SYMBOL(__copy_user_inatomic)
b __copy_user_common
li t7, 1
END(__copy_user_inatomic)
/*
* A combined memcpy/__copy_user
* __copy_user sets len to 0 for success; else to an upper bound of
* the number of uncopied bytes.
* memcpy sets v0 to dst.
*/
.align 5
LEAF(memcpy) /* a0=dst a1=src a2=len */
EXPORT_SYMBOL(memcpy)
move v0, dst /* return value */
__memcpy:
FEXPORT(__copy_user)
EXPORT_SYMBOL(__copy_user)
li t7, 0 /* not inatomic */
__copy_user_common:
/*
* Note: dst & src may be unaligned, len may be 0
* Temps
*/
#
# Octeon doesn't care if the destination is unaligned. The hardware
# can fix it faster than we can special case the assembly.
#
pref 0, 0(src)
sltu t0, len, NBYTES # Check if < 1 word
bnez t0, copy_bytes_checklen
and t0, src, ADDRMASK # Check if src unaligned
bnez t0, src_unaligned
sltu t0, len, 4*NBYTES # Check if < 4 words
bnez t0, less_than_4units
sltu t0, len, 8*NBYTES # Check if < 8 words
bnez t0, less_than_8units
sltu t0, len, 16*NBYTES # Check if < 16 words
bnez t0, cleanup_both_aligned
sltu t0, len, 128+1 # Check if len < 129
bnez t0, 1f # Skip prefetch if len is too short
sltu t0, len, 256+1 # Check if len < 257
bnez t0, 1f # Skip prefetch if len is too short
pref 0, 128(src) # We must not prefetch invalid addresses
#
# This is where we loop if there is more than 128 bytes left
2: pref 0, 256(src) # We must not prefetch invalid addresses
#
# This is where we loop if we can't prefetch anymore
1:
EXC( LOAD t0, UNIT(0)(src), l_exc)
EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
SUB len, len, 16*NBYTES
EXC( STORE t0, UNIT(0)(dst), s_exc_p16u)
EXC( STORE t1, UNIT(1)(dst), s_exc_p15u)
EXC( STORE t2, UNIT(2)(dst), s_exc_p14u)
EXC( STORE t3, UNIT(3)(dst), s_exc_p13u)
EXC( LOAD t0, UNIT(4)(src), l_exc_copy)
EXC( LOAD t1, UNIT(5)(src), l_exc_copy)
EXC( LOAD t2, UNIT(6)(src), l_exc_copy)
EXC( LOAD t3, UNIT(7)(src), l_exc_copy)
EXC( STORE t0, UNIT(4)(dst), s_exc_p12u)
EXC( STORE t1, UNIT(5)(dst), s_exc_p11u)
EXC( STORE t2, UNIT(6)(dst), s_exc_p10u)
ADD src, src, 16*NBYTES
EXC( STORE t3, UNIT(7)(dst), s_exc_p9u)
ADD dst, dst, 16*NBYTES
EXC( LOAD t0, UNIT(-8)(src), l_exc_copy_rewind16)
EXC( LOAD t1, UNIT(-7)(src), l_exc_copy_rewind16)
EXC( LOAD t2, UNIT(-6)(src), l_exc_copy_rewind16)
EXC( LOAD t3, UNIT(-5)(src), l_exc_copy_rewind16)
EXC( STORE t0, UNIT(-8)(dst), s_exc_p8u)
EXC( STORE t1, UNIT(-7)(dst), s_exc_p7u)
EXC( STORE t2, UNIT(-6)(dst), s_exc_p6u)
EXC( STORE t3, UNIT(-5)(dst), s_exc_p5u)
EXC( LOAD t0, UNIT(-4)(src), l_exc_copy_rewind16)
EXC( LOAD t1, UNIT(-3)(src), l_exc_copy_rewind16)
EXC( LOAD t2, UNIT(-2)(src), l_exc_copy_rewind16)
EXC( LOAD t3, UNIT(-1)(src), l_exc_copy_rewind16)
EXC( STORE t0, UNIT(-4)(dst), s_exc_p4u)
EXC( STORE t1, UNIT(-3)(dst), s_exc_p3u)
EXC( STORE t2, UNIT(-2)(dst), s_exc_p2u)
EXC( STORE t3, UNIT(-1)(dst), s_exc_p1u)
sltu t0, len, 256+1 # See if we can prefetch more
beqz t0, 2b
sltu t0, len, 128 # See if we can loop more time
beqz t0, 1b
nop
#
# Jump here if there are less than 16*NBYTES left.
#
cleanup_both_aligned:
beqz len, done
sltu t0, len, 8*NBYTES
bnez t0, less_than_8units
nop
EXC( LOAD t0, UNIT(0)(src), l_exc)
EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
SUB len, len, 8*NBYTES
EXC( STORE t0, UNIT(0)(dst), s_exc_p8u)
EXC( STORE t1, UNIT(1)(dst), s_exc_p7u)
EXC( STORE t2, UNIT(2)(dst), s_exc_p6u)
EXC( STORE t3, UNIT(3)(dst), s_exc_p5u)
EXC( LOAD t0, UNIT(4)(src), l_exc_copy)
EXC( LOAD t1, UNIT(5)(src), l_exc_copy)
EXC( LOAD t2, UNIT(6)(src), l_exc_copy)
EXC( LOAD t3, UNIT(7)(src), l_exc_copy)
EXC( STORE t0, UNIT(4)(dst), s_exc_p4u)
EXC( STORE t1, UNIT(5)(dst), s_exc_p3u)
EXC( STORE t2, UNIT(6)(dst), s_exc_p2u)
EXC( STORE t3, UNIT(7)(dst), s_exc_p1u)
ADD src, src, 8*NBYTES
beqz len, done
ADD dst, dst, 8*NBYTES
#
# Jump here if there are less than 8*NBYTES left.
#
less_than_8units:
sltu t0, len, 4*NBYTES
bnez t0, less_than_4units
nop
EXC( LOAD t0, UNIT(0)(src), l_exc)
EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
SUB len, len, 4*NBYTES
EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
ADD src, src, 4*NBYTES
beqz len, done
ADD dst, dst, 4*NBYTES
#
# Jump here if there are less than 4*NBYTES left. This means
# we may need to copy up to 3 NBYTES words.
#
less_than_4units:
sltu t0, len, 1*NBYTES
bnez t0, copy_bytes_checklen
nop
#
# 1) Copy NBYTES, then check length again
#
EXC( LOAD t0, 0(src), l_exc)
SUB len, len, NBYTES
sltu t1, len, 8
EXC( STORE t0, 0(dst), s_exc_p1u)
ADD src, src, NBYTES
bnez t1, copy_bytes_checklen
ADD dst, dst, NBYTES
#
# 2) Copy NBYTES, then check length again
#
EXC( LOAD t0, 0(src), l_exc)
SUB len, len, NBYTES
sltu t1, len, 8
EXC( STORE t0, 0(dst), s_exc_p1u)
ADD src, src, NBYTES
bnez t1, copy_bytes_checklen
ADD dst, dst, NBYTES
#
# 3) Copy NBYTES, then check length again
#
EXC( LOAD t0, 0(src), l_exc)
SUB len, len, NBYTES
ADD src, src, NBYTES
ADD dst, dst, NBYTES
b copy_bytes_checklen
EXC( STORE t0, -8(dst), s_exc_p1u)
src_unaligned:
#define rem t8
SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter
beqz t0, cleanup_src_unaligned
and rem, len, (4*NBYTES-1) # rem = len % 4*NBYTES
1:
/*
* Avoid consecutive LD*'s to the same register since some mips
* implementations can't issue them in the same cycle.
* It's OK to load FIRST(N+1) before REST(N) because the two addresses
* are to the same unit (unless src is aligned, but it's not).
*/
EXC( LDFIRST t0, FIRST(0)(src), l_exc)
EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy)
SUB len, len, 4*NBYTES
EXC( LDREST t0, REST(0)(src), l_exc_copy)
EXC( LDREST t1, REST(1)(src), l_exc_copy)
EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy)
EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy)
EXC( LDREST t2, REST(2)(src), l_exc_copy)
EXC( LDREST t3, REST(3)(src), l_exc_copy)
ADD src, src, 4*NBYTES
EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
bne len, rem, 1b
ADD dst, dst, 4*NBYTES
cleanup_src_unaligned:
beqz len, done
and rem, len, NBYTES-1 # rem = len % NBYTES
beq rem, len, copy_bytes
nop
1:
EXC( LDFIRST t0, FIRST(0)(src), l_exc)
EXC( LDREST t0, REST(0)(src), l_exc_copy)
SUB len, len, NBYTES
EXC( STORE t0, 0(dst), s_exc_p1u)
ADD src, src, NBYTES
bne len, rem, 1b
ADD dst, dst, NBYTES
copy_bytes_checklen:
beqz len, done
nop
copy_bytes:
/* 0 < len < NBYTES */
#define COPY_BYTE(N) \
EXC( lb t0, N(src), l_exc); \
SUB len, len, 1; \
beqz len, done; \
EXC( sb t0, N(dst), s_exc_p1)
COPY_BYTE(0)
COPY_BYTE(1)
COPY_BYTE(2)
COPY_BYTE(3)
COPY_BYTE(4)
COPY_BYTE(5)
EXC( lb t0, NBYTES-2(src), l_exc)
SUB len, len, 1
jr ra
EXC( sb t0, NBYTES-2(dst), s_exc_p1)
done:
jr ra
nop
END(memcpy)
l_exc_copy_rewind16:
/* Rewind src and dst by 16*NBYTES for l_exc_copy */
SUB src, src, 16*NBYTES
SUB dst, dst, 16*NBYTES
l_exc_copy:
/*
* Copy bytes from src until faulting load address (or until a
* lb faults)
*
* When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
* may be more than a byte beyond the last address.
* Hence, the lb below may get an exception.
*
* Assumes src < THREAD_BUADDR($28)
*/
LOAD t0, TI_TASK($28)
LOAD t0, THREAD_BUADDR(t0)
1:
EXC( lb t1, 0(src), l_exc)
ADD src, src, 1
sb t1, 0(dst) # can't fault -- we're copy_from_user
bne src, t0, 1b
ADD dst, dst, 1
l_exc:
LOAD t0, TI_TASK($28)
LOAD t0, THREAD_BUADDR(t0) # t0 is just past last good address
SUB len, AT, t0 # len number of uncopied bytes
bnez t7, 2f /* Skip the zeroing out part if inatomic */
/*
* Here's where we rely on src and dst being incremented in tandem,
* See (3) above.
* dst += (fault addr - src) to put dst at first byte to clear
*/
ADD dst, t0 # compute start address in a1
SUB dst, src
/*
* Clear len bytes starting at dst. Can't call __bzero because it
* might modify len. An inefficient loop for these rare times...
*/
beqz len, done
SUB src, len, 1
1: sb zero, 0(dst)
ADD dst, dst, 1
bnez src, 1b
SUB src, src, 1
2: jr ra
nop
#define SEXC(n) \
s_exc_p ## n ## u: \
jr ra; \
ADD len, len, n*NBYTES
SEXC(16)
SEXC(15)
SEXC(14)
SEXC(13)
SEXC(12)
SEXC(11)
SEXC(10)
SEXC(9)
SEXC(8)
SEXC(7)
SEXC(6)
SEXC(5)
SEXC(4)
SEXC(3)
SEXC(2)
SEXC(1)
s_exc_p1:
jr ra
ADD len, len, 1
s_exc:
jr ra
nop
.align 5
LEAF(memmove)
EXPORT_SYMBOL(memmove)
ADD t0, a0, a2
ADD t1, a1, a2
sltu t0, a1, t0 # dst + len <= src -> memcpy
sltu t1, a0, t1 # dst >= src + len -> memcpy
and t0, t1
beqz t0, __memcpy
move v0, a0 /* return value */
beqz a2, r_out
END(memmove)
/* fall through to __rmemcpy */
LEAF(__rmemcpy) /* a0=dst a1=src a2=len */
sltu t0, a1, a0
beqz t0, r_end_bytes_up # src >= dst
nop
ADD a0, a2 # dst = dst + len
ADD a1, a2 # src = src + len
r_end_bytes:
lb t0, -1(a1)
SUB a2, a2, 0x1
sb t0, -1(a0)
SUB a1, a1, 0x1
bnez a2, r_end_bytes
SUB a0, a0, 0x1
r_out:
jr ra
move a2, zero
r_end_bytes_up:
lb t0, (a1)
SUB a2, a2, 0x1
sb t0, (a0)
ADD a1, a1, 0x1
bnez a2, r_end_bytes_up
ADD a0, a0, 0x1
jr ra
move a2, zero
END(__rmemcpy)
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