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alpha: get rid of tail-zeroing in __copy_user()

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... and adjust copy_from_user() accordingly

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-09-10 16:21:34 -04:00
parent 8630c32275
commit 085354f907
3 changed files with 7 additions and 41 deletions
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9
arch/alpha/include/asm/uaccess.h
View file

@ -396,11 +396,12 @@ copy_to_user(void __user *to, const void *from, long n)
extern inline long
copy_from_user(void *to, const void __user *from, long n)
{
long res = n;
if (likely(__access_ok((unsigned long)from, n, get_fs())))
n = __copy_tofrom_user_nocheck(to, (__force void *)from, n);
else
memset(to, 0, n);
return n;
res = __copy_from_user_inatomic(to, from, n);
if (unlikely(res))
memset(to + (n - res), 0, res);
return res;
}
extern void __do_clear_user(void);

16
arch/alpha/lib/copy_user.S
View file

@ -124,22 +124,8 @@ $65:
bis $31,$31,$0
$41:
$35:
$exitin:
$exitout:
ret $31,($28),1
$exitin:
/* A stupid byte-by-byte zeroing of the rest of the output
buffer. This cures security holes by never leaving
random kernel data around to be copied elsewhere. */
mov $0,$1
$101:
EXO ( ldq_u $2,0($6) )
subq $1,1,$1
mskbl $2,$6,$2
EXO ( stq_u $2,0($6) )
addq $6,1,$6
bgt $1,$101
ret $31,($28),1
.end __copy_user

23
arch/alpha/lib/ev6-copy_user.S
View file

@ -227,33 +227,12 @@ $dirtyentry:
bgt $0,$onebyteloop # U .. .. .. : U L U L
$zerolength:
$exitin:
$exitout: # Destination for exception recovery(?)
nop # .. .. .. E
nop # .. .. E ..
nop # .. E .. ..
ret $31,($28),1 # L0 .. .. .. : L U L U
$exitin:
/* A stupid byte-by-byte zeroing of the rest of the output
buffer. This cures security holes by never leaving
random kernel data around to be copied elsewhere. */
nop
nop
nop
mov $0,$1
$101:
EXO ( stb $31,0($6) ) # L
subq $1,1,$1 # E
addq $6,1,$6 # E
bgt $1,$101 # U
nop
nop
nop
ret $31,($28),1 # L0
.end __copy_user