On Fri, Aug 16, 2019 at 11:42 AM Bart Van Assche <[email protected]> wrote: > > On 8/15/19 7:54 PM, Ming Lei wrote: > > It is reported that sysfs buffer overflow can be triggered in case > > of too many CPU cores(>841 on 4K PAGE_SIZE) when showing CPUs in > > blk_mq_hw_sysfs_cpus_show(). > > > > So use cpumap_print_to_pagebuf() to print the info and fix the potential > > buffer overflow issue. > > > > Cc: [email protected] > > Cc: Mark Ray <[email protected]> > > Cc: Greg KH <[email protected]> > > Fixes: 676141e48af7("blk-mq: don't dump CPU -> hw queue map on driver load") > > Signed-off-by: Ming Lei <[email protected]> > > --- > > block/blk-mq-sysfs.c | 15 +-------------- > > 1 file changed, 1 insertion(+), 14 deletions(-) > > > > diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c > > index d6e1a9bd7131..4d0d32377ba3 100644 > > --- a/block/blk-mq-sysfs.c > > +++ b/block/blk-mq-sysfs.c > > @@ -166,20 +166,7 @@ static ssize_t > > blk_mq_hw_sysfs_nr_reserved_tags_show(struct blk_mq_hw_ctx *hctx, > > > > static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx *hctx, char > > *page) > > { > > - unsigned int i, first = 1; > > - ssize_t ret = 0; > > - > > - for_each_cpu(i, hctx->cpumask) { > > - if (first) > > - ret += sprintf(ret + page, "%u", i); > > - else > > - ret += sprintf(ret + page, ", %u", i); > > - > > - first = 0; > > - } > > - > > - ret += sprintf(ret + page, "\n"); > > - return ret; > > + return cpumap_print_to_pagebuf(true, page, hctx->cpumask); > > } > > > > static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = { > > Although this patch looks fine to me, shouldn't this attribute be > documented under Documentation/ABI/?
That is another problem, not closely related with this buffer-overflow issue. I suggest to fix the buffer overflow first, which is triggered from userspace. Thanks, Ming Lei
