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From: Li Nan <linan122@huawei.com>
To: <tj@kernel.org>, <josef@toxicpanda.com>, <axboe@kernel.dk>
Cc: <cgroups@vger.kernel.org>, <linux-block@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linan122@huawei.com>,
	<yukuai3@huawei.com>, <yi.zhang@huawei.com>
Subject: [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs()
Date: Thu, 24 Nov 2022 22:06:34 +0800	[thread overview]
Message-ID: <20221124140635.695205-1-linan122@huawei.com> (raw)

echo max of u64 to cost.model can cause divide by 0 error.

  # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model

  divide error: 0000 [#1] PREEMPT SMP
  RIP: 0010:calc_lcoefs+0x4c/0xc0
  Call Trace:
   <TASK>
   ioc_refresh_params+0x2b3/0x4f0
   ioc_cost_model_write+0x3cb/0x4c0
   ? _copy_from_iter+0x6d/0x6c0
   ? kernfs_fop_write_iter+0xfc/0x270
   cgroup_file_write+0xa0/0x200
   kernfs_fop_write_iter+0x17d/0x270
   vfs_write+0x414/0x620
   ksys_write+0x73/0x160
   __x64_sys_write+0x1e/0x30
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x63/0xcd

calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL,
overflow would happen if bps plus IOC_PAGE_SIZE is greater than
ULLONG_MAX, it can cause divide by 0 error.I_LCOEF_MAX is introduced to
prevent it.

Signed-off-by: Li Nan <linan122@huawei.com>
---
 block/blk-iocost.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index f01359906c83..a38a5324bf10 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -306,6 +306,9 @@ enum {
 	IOC_PAGE_SIZE		= 1 << IOC_PAGE_SHIFT,
 	IOC_SECT_TO_PAGE_SHIFT	= IOC_PAGE_SHIFT - SECTOR_SHIFT,
 
+	/* avoid overflow */
+	I_LCOEF_MAX		= ULLONG_MAX - IOC_PAGE_SIZE,
+
 	/* if apart further than 16M, consider randio for linear model */
 	LCOEF_RANDIO_PAGES	= 4096,
 };
@@ -3406,6 +3409,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 			goto einval;
 		if (match_u64(&args[0], &v))
 			goto einval;
+		if (v > I_LCOEF_MAX)
+			goto einval;
 		u[tok] = v;
 		user = true;
 	}
-- 
2.31.1


WARNING: multiple messages have this Message-ID (diff)
From: Li Nan <linan122@huawei.com>
To: tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk
Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linan122@huawei.com,
	yukuai3@huawei.com, yi.zhang@huawei.com
Subject: [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs()
Date: Thu, 24 Nov 2022 22:06:34 +0800	[thread overview]
Message-ID: <20221124140635.695205-1-linan122@huawei.com> (raw)

echo max of u64 to cost.model can cause divide by 0 error.

  # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model

  divide error: 0000 [#1] PREEMPT SMP
  RIP: 0010:calc_lcoefs+0x4c/0xc0
  Call Trace:
   <TASK>
   ioc_refresh_params+0x2b3/0x4f0
   ioc_cost_model_write+0x3cb/0x4c0
   ? _copy_from_iter+0x6d/0x6c0
   ? kernfs_fop_write_iter+0xfc/0x270
   cgroup_file_write+0xa0/0x200
   kernfs_fop_write_iter+0x17d/0x270
   vfs_write+0x414/0x620
   ksys_write+0x73/0x160
   __x64_sys_write+0x1e/0x30
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x63/0xcd

calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL,
overflow would happen if bps plus IOC_PAGE_SIZE is greater than
ULLONG_MAX, it can cause divide by 0 error.I_LCOEF_MAX is introduced to
prevent it.

Signed-off-by: Li Nan <linan122@huawei.com>
---
 block/blk-iocost.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index f01359906c83..a38a5324bf10 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -306,6 +306,9 @@ enum {
 	IOC_PAGE_SIZE		= 1 << IOC_PAGE_SHIFT,
 	IOC_SECT_TO_PAGE_SHIFT	= IOC_PAGE_SHIFT - SECTOR_SHIFT,
 
+	/* avoid overflow */
+	I_LCOEF_MAX		= ULLONG_MAX - IOC_PAGE_SIZE,
+
 	/* if apart further than 16M, consider randio for linear model */
 	LCOEF_RANDIO_PAGES	= 4096,
 };
@@ -3406,6 +3409,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 			goto einval;
 		if (match_u64(&args[0], &v))
 			goto einval;
+		if (v > I_LCOEF_MAX)
+			goto einval;
 		u[tok] = v;
 		user = true;
 	}
-- 
2.31.1


             reply	other threads:[~2022-11-24 13:45 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-24 14:06 Li Nan [this message]
2022-11-24 14:06 ` [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs() Li Nan
2022-11-24 14:06 ` [PATCH -next 2/2] blk-iocost: change div64_u64 to DIV64_U64_ROUND_UP in ioc_refresh_params() Li Nan
2022-11-24 14:06   ` Li Nan
2022-11-25 10:14   ` Andreas Herrmann
2022-11-25  9:52 ` [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs() Andreas Herrmann

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