Commit 124afe77 authored by Antoine Tenart's avatar Antoine Tenart Committed by Paolo Abeni
Browse files

net: sysctl: allow dump_cpumask to handle higher numbers of CPUs 



This fixes the output of rps_default_mask and flow_limit_cpu_bitmap when
the CPU count is > 448, as it was truncated.

The underlying values are actually stored correctly when writing to
these sysctl but displaying them uses a fixed length temporary buffer in
dump_cpumask. This buffer can be too small if the CPU count is > 448.

Fix this by dynamically allocating the buffer in dump_cpumask, using a
guesstimate of what we need.

Signed-off-by: default avatarAntoine Tenart <atenart@kernel.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent a8cc8fa1

net/core/sysctl_net_core.c

+23 −9
Original line number Diff line number Diff line
@@ -51,22 +51,32 @@ int sysctl_devconf_inherit_init_net __read_mostly; 
EXPORT_SYMBOL(sysctl_devconf_inherit_init_net);



#if IS_ENABLED(CONFIG_NET_FLOW_LIMIT) || IS_ENABLED(CONFIG_RPS)

static void dump_cpumask(void *buffer, size_t *lenp, loff_t *ppos,

static int dump_cpumask(void *buffer, size_t *lenp, loff_t *ppos,

			struct cpumask *mask)

{

	char kbuf[128];

	char *kbuf;

	int len;



	if (*ppos || !*lenp) {

		*lenp = 0;

		return;

		return 0;

	}



	/* CPUs are displayed as a hex bitmap + a comma between each groups of 8

	 * nibbles (except the last one which has a newline instead).

	 * Guesstimate the buffer size at the group granularity level.

	 */

	len = min(DIV_ROUND_UP(nr_cpumask_bits, 32) * (8 + 1), *lenp);

	kbuf = kmalloc(len, GFP_KERNEL);

	if (!kbuf) {

		*lenp = 0;

		return -ENOMEM;

	}



	len = min(sizeof(kbuf), *lenp);

	len = scnprintf(kbuf, len, "%*pb", cpumask_pr_args(mask));

	if (!len) {

		*lenp = 0;

		return;

		goto free_buf;

	}



	/* scnprintf writes a trailing null char not counted in the returned
@@ -76,6 +86,10 @@ static void dump_cpumask(void *buffer, size_t *lenp, loff_t *ppos, 
	memcpy(buffer, kbuf, len);

	*lenp = len;

	*ppos += len;



free_buf:

	kfree(kbuf);

	return 0;

}

#endif
@@ -119,7 +133,7 @@ static int rps_default_mask_sysctl(const struct ctl_table *table, int write, 
		if (err)

			goto done;

	} else {

		dump_cpumask(buffer, lenp, ppos,

		err = dump_cpumask(buffer, lenp, ppos,

				   net->core.rps_default_mask ? : cpu_none_mask);

	}
@@ -249,7 +263,7 @@ static int flow_limit_cpu_sysctl(const struct ctl_table *table, int write, 
		}

		rcu_read_unlock();



		dump_cpumask(buffer, lenp, ppos, mask);

		ret = dump_cpumask(buffer, lenp, ppos, mask);

	}



done: