https://github.com/torvalds/linux
Revision 573b3aa6940661dc50c383213d428c27df78be7c authored by Yonghong Song on 30 July 2018, 15:49:03 UTC, committed by Daniel Borkmann on 30 July 2018, 22:37:09 UTC
I hit the following problem when I tried to use bpftool
to dump a percpu array.
$ sudo ./bpftool map show
61: percpu_array name stub flags 0x0
key 4B value 4B max_entries 1 memlock 4096B
...
$ sudo ./bpftool map dump id 61
bpftool: malloc.c:2406: sysmalloc: Assertion
`(old_top == initial_top (av) && old_size == 0) || \
((unsigned long) (old_size) >= MINSIZE && \
prev_inuse (old_top) && \
((unsigned long) old_end & (pagesize - 1)) == 0)'
failed.
Aborted
Further debugging revealed that this is due to
miscommunication between bpftool and kernel.
For example, for the above percpu_array with value size of 4B.
The map info returned to user space has value size of 4B.
In bpftool, the values array for lookup is allocated like:
info->value_size * get_possible_cpus() = 4 * get_possible_cpus()
In kernel (kernel/bpf/syscall.c), the values array size is
rounded up to multiple of 8.
round_up(map->value_size, 8) * num_possible_cpus()
= 8 * num_possible_cpus()
So when kernel copies the values to user buffer, the kernel will
overwrite beyond user buffer boundary.
This patch fixed the issue by allocating and stepping through
percpu map value array properly in bpftool.
Fixes: 71bb428fe2c19 ("tools: bpf: add bpftool")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
1 parent 61f4b23
Tip revision: 573b3aa6940661dc50c383213d428c27df78be7c authored by Yonghong Song on 30 July 2018, 15:49:03 UTC
tools/bpftool: fix a percpu_array map dump problem
tools/bpftool: fix a percpu_array map dump problem
Tip revision: 573b3aa
op-8.h
/* Software floating-point emulation.
Basic eight-word fraction declaration and manipulation.
Copyright (C) 1997,1998,1999 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson (rth@cygnus.com),
Jakub Jelinek (jj@ultra.linux.cz) and
Peter Maydell (pmaydell@chiark.greenend.org.uk).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#ifndef __MATH_EMU_OP_8_H__
#define __MATH_EMU_OP_8_H__
/* We need just a few things from here for op-4, if we ever need some
other macros, they can be added. */
#define _FP_FRAC_DECL_8(X) _FP_W_TYPE X##_f[8]
#define _FP_FRAC_HIGH_8(X) (X##_f[7])
#define _FP_FRAC_LOW_8(X) (X##_f[0])
#define _FP_FRAC_WORD_8(X,w) (X##_f[w])
#define _FP_FRAC_SLL_8(X,N) \
do { \
_FP_I_TYPE _up, _down, _skip, _i; \
_skip = (N) / _FP_W_TYPE_SIZE; \
_up = (N) % _FP_W_TYPE_SIZE; \
_down = _FP_W_TYPE_SIZE - _up; \
if (!_up) \
for (_i = 7; _i >= _skip; --_i) \
X##_f[_i] = X##_f[_i-_skip]; \
else \
{ \
for (_i = 7; _i > _skip; --_i) \
X##_f[_i] = X##_f[_i-_skip] << _up \
| X##_f[_i-_skip-1] >> _down; \
X##_f[_i--] = X##_f[0] << _up; \
} \
for (; _i >= 0; --_i) \
X##_f[_i] = 0; \
} while (0)
#define _FP_FRAC_SRL_8(X,N) \
do { \
_FP_I_TYPE _up, _down, _skip, _i; \
_skip = (N) / _FP_W_TYPE_SIZE; \
_down = (N) % _FP_W_TYPE_SIZE; \
_up = _FP_W_TYPE_SIZE - _down; \
if (!_down) \
for (_i = 0; _i <= 7-_skip; ++_i) \
X##_f[_i] = X##_f[_i+_skip]; \
else \
{ \
for (_i = 0; _i < 7-_skip; ++_i) \
X##_f[_i] = X##_f[_i+_skip] >> _down \
| X##_f[_i+_skip+1] << _up; \
X##_f[_i++] = X##_f[7] >> _down; \
} \
for (; _i < 8; ++_i) \
X##_f[_i] = 0; \
} while (0)
/* Right shift with sticky-lsb.
* What this actually means is that we do a standard right-shift,
* but that if any of the bits that fall off the right hand side
* were one then we always set the LSbit.
*/
#define _FP_FRAC_SRS_8(X,N,size) \
do { \
_FP_I_TYPE _up, _down, _skip, _i; \
_FP_W_TYPE _s; \
_skip = (N) / _FP_W_TYPE_SIZE; \
_down = (N) % _FP_W_TYPE_SIZE; \
_up = _FP_W_TYPE_SIZE - _down; \
for (_s = _i = 0; _i < _skip; ++_i) \
_s |= X##_f[_i]; \
_s |= X##_f[_i] << _up; \
/* s is now != 0 if we want to set the LSbit */ \
if (!_down) \
for (_i = 0; _i <= 7-_skip; ++_i) \
X##_f[_i] = X##_f[_i+_skip]; \
else \
{ \
for (_i = 0; _i < 7-_skip; ++_i) \
X##_f[_i] = X##_f[_i+_skip] >> _down \
| X##_f[_i+_skip+1] << _up; \
X##_f[_i++] = X##_f[7] >> _down; \
} \
for (; _i < 8; ++_i) \
X##_f[_i] = 0; \
/* don't fix the LSB until the very end when we're sure f[0] is stable */ \
X##_f[0] |= (_s != 0); \
} while (0)
#endif
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