linux-stable.git/drivers/md/bcache/sysfs.c, branch linux-4.19.y

bcache: prevent potential division by zero error

2023-12-08T07:43:24+00:00

commit 2c7f497ac274a14330208b18f6f734000868ebf9 upstream.

In SHOW(), the variable 'n' is of type 'size_t.' While there is a
conditional check to verify that 'n' is not equal to zero before
executing the 'do_div' macro, concerns arise regarding potential
division by zero error in 64-bit environments.

The concern arises when 'n' is 64 bits in size, greater than zero, and
the lower 32 bits of it are zeros. In such cases, the conditional check
passes because 'n' is non-zero, but the 'do_div' macro casts 'n' to
'uint32_t,' effectively truncating it to its lower 32 bits.
Consequently, the 'n' value becomes zero.

To fix this potential division by zero error and ensure precise
division handling, this commit replaces the 'do_div' macro with
div64_u64(). div64_u64() is designed to work with 64-bit operands,
guaranteeing that division is performed correctly.

This change enhances the robustness of the code, ensuring that division
operations yield accurate results in all scenarios, eliminating the
possibility of division by zero, and improving compatibility across
different 64-bit environments.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Rand Deeb 
Cc:  
Signed-off-by: Coly Li 
Link: https://lore.kernel.org/r/20231120052503.6122-5-colyli@suse.de
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: add readahead cache policy options via sysfs interface

2020-02-11T12:34:08+00:00

commit 038ba8cc1bffc51250add4a9b9249d4331576d8f upstream.

In year 2007 high performance SSD was still expensive, in order to
save more space for real workload or meta data, the readahead I/Os
for non-meta data was bypassed and not cached on SSD.

In now days, SSD price drops a lot and people can find larger size
SSD with more comfortable price. It is unncessary to alway bypass
normal readahead I/Os to save SSD space for now.

This patch adds options for readahead data cache policies via sysfs
file /sys/block/bcache/readahead_cache_policy, the options are,
- "all": cache all readahead data I/Os.
- "meta-only": only cache meta data, and bypass other regular I/Os.

If users want to make bcache continue to only cache readahead request
for metadata and bypass regular data readahead, please set "meta-only"
to this sysfs file. By default, bcache will back to cache all read-
ahead requests now.

Cc: stable@vger.kernel.org
Signed-off-by: Coly Li 
Acked-by: Eric Wheeler 
Cc: Michael Lyle 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: fix input overflow to writeback_rate_minimum

2019-11-06T12:05:20+00:00

[ Upstream commit dab71b2db98dcdd4657d151b01a7be88ce10f9d1 ]

dc->writeback_rate_minimum is type unsigned integer variable, it is set
via sysfs interface, and converte from input string to unsigned integer
by d_strtoul_nonzero(). When the converted input value is larger than
UINT_MAX, overflow to unsigned integer happens.

This patch fixes the overflow by using sysfs_strotoul_clamp() to
convert input string and limit the value in range [1, UINT_MAX], then
the overflow can be avoided.

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: fix mistaken sysfs entry for io_error counter

2019-07-26T07:14:21+00:00

commit 5461999848e0462c14f306a62923d22de820a59c upstream.

In bch_cached_dev_files[] from driver/md/bcache/sysfs.c, sysfs_errors is
incorrectly inserted in. The correct entry should be sysfs_io_errors.

This patch fixes the problem and now I/O errors of cached device can be
read from /sys/block/bcache/bcache/io_errors.

Fixes: c7b7bd07404c5 ("bcache: add io_disable to struct cached_dev")
Signed-off-by: Coly Li 
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: only set BCACHE_DEV_WB_RUNNING when cached device attached

2019-06-19T06:18:00+00:00

commit 1f0ffa67349c56ea54c03ccfd1e073c990e7411e upstream.

When people set a writeback percent via sysfs file,
  /sys/block/bcache/bcache/writeback_percent
current code directly sets BCACHE_DEV_WB_RUNNING to dc->disk.flags
and schedules kworker dc->writeback_rate_update.

If there is no cache set attached to, the writeback kernel thread is
not running indeed, running dc->writeback_rate_update does not make
sense and may cause NULL pointer deference when reference cache set
pointer inside update_writeback_rate().

This patch checks whether the cache set point (dc->disk.c) is NULL in
sysfs interface handler, and only set BCACHE_DEV_WB_RUNNING and
schedule dc->writeback_rate_update when dc->disk.c is not NULL (it
means the cache device is attached to a cache set).

This problem might be introduced from initial bcache commit, but
commit 3fd47bfe55b0 ("bcache: stop dc->writeback_rate_update properly")
changes part of the original code piece, so I add 'Fixes: 3fd47bfe55b0'
to indicate from which commit this patch can be applied.

Fixes: 3fd47bfe55b0 ("bcache: stop dc->writeback_rate_update properly")
Reported-by: Bjørn Forsman 
Signed-off-by: Coly Li 
Reviewed-by: Bjørn Forsman 
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: fix potential div-zero error of writeback_rate_p_term_inverse

2019-04-05T20:33:17+00:00

[ Upstream commit 5b5fd3c94eef69dcfaa8648198e54c92e5687d6d ]

Current code already uses d_strtoul_nonzero() to convert input string
to an unsigned integer, to make sure writeback_rate_p_term_inverse
won't be zero value. But overflow may happen when converting input
string to an unsigned integer value by d_strtoul_nonzero(), then
dc->writeback_rate_p_term_inverse can still be set to 0 even if the
sysfs file input value is not zero, e.g. 4294967296 (a.k.a UINT_MAX+1).

If dc->writeback_rate_p_term_inverse is set to 0, it might cause a
dev-zero error in following code from __update_writeback_rate(),
	int64_t proportional_scaled =
		div_s64(error, dc->writeback_rate_p_term_inverse);

This patch replaces d_strtoul_nonzero() by sysfs_strtoul_clamp() and
limit the value range in [1, UINT_MAX]. Then the unsigned integer
overflow and dev-zero error can be avoided.

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: fix potential div-zero error of writeback_rate_i_term_inverse

2019-04-05T20:33:09+00:00

[ Upstream commit c3b75a2199cdbfc1c335155fe143d842604b1baa ]

dc->writeback_rate_i_term_inverse can be set via sysfs interface. It is
in type unsigned int, and convert from input string by d_strtoul(). The
problem is d_strtoul() does not check valid range of the input, if
4294967296 is written into sysfs file writeback_rate_i_term_inverse,
an overflow of unsigned integer will happen and value 0 is set to
dc->writeback_rate_i_term_inverse.

In writeback.c:__update_writeback_rate(), there are following lines of
code,
      integral_scaled = div_s64(dc->writeback_rate_integral,
                      dc->writeback_rate_i_term_inverse);
If dc->writeback_rate_i_term_inverse is set to 0 via sysfs interface,
a div-zero error might be triggered in the above code.

Therefore we need to add a range limitation in the sysfs interface,
this is what this patch does, use sysfs_stroul_clamp() to replace
d_strtoul() and restrict the input range in [1, UINT_MAX].

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: fix input overflow to sequential_cutoff

2019-04-05T20:33:09+00:00

[ Upstream commit 8c27a3953e92eb0b22dbb03d599f543a05f9574e ]

People may set sequential_cutoff of a cached device via sysfs file,
but current code does not check input value overflow. E.g. if value
4294967295 (UINT_MAX) is written to file sequential_cutoff, its value
is 4GB, but if 4294967296 (UINT_MAX + 1) is written into, its value
will be 0. This is an unexpected behavior.

This patch replaces d_strtoi_h() by sysfs_strtoul_clamp() to convert
input string to unsigned integer value, and limit its range in
[0, UINT_MAX]. Then the input overflow can be fixed.

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: fix input overflow to cache set sysfs file io_error_halflife

2019-04-05T20:33:09+00:00

[ Upstream commit a91fbda49f746119828f7e8ad0f0aa2ab0578f65 ]

Cache set sysfs entry io_error_halflife is used to set c->error_decay.
c->error_decay is in type unsigned int, and it is converted by
strtoul_or_return(), therefore overflow to c->error_decay is possible
for a large input value.

This patch fixes the overflow by using strtoul_safe_clamp() to convert
input string to an unsigned long value in range [0, UINT_MAX], then
divides by 88 and set it to c->error_decay.

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: Populate writeback_rate_minimum attribute

2018-11-13T19:08:22+00:00

[ Upstream commit 7567c2a2ad9e80a2ce977eef535e64b61899633e ]

Forgot to include the maintainers with my first email.

Somewhere between Michael Lyle's original
"bcache: PI controller for writeback rate V2" patch dated 07 Sep 2017
and 1d316e6 bcache: implement PI controller for writeback rate,
the mapping of the writeback_rate_minimum attribute was dropped.

Re-add the missing sysfs writeback_rate_minimum attribute mapping to
"allow the user to specify a minimum rate at which dirty blocks are
retired."

Fixes: 1d316e6 ("bcache: implement PI controller for writeback rate")
Signed-off-by: Ben Peddell 
Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman