| Message ID | 20221124140635.695205-1-linan122@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next,1/2] blk-iocost: fix divide by 0 error in calc_lcoefs() | expand |
On Thu, Nov 24, 2022 at 10:06:34PM +0800, Li Nan wrote: > 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(+) Looks good. Reviewed-by: Andreas Herrmann <aherrmann@suse.de> > 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 >
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; }
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(+)