Commit 005a79e5 authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Linus Torvalds
Browse files

mm/slub: fix endianness bug for alloc/free_traces attributes 

On big-endian s390, the alloc/free_traces attributes produce endless
output, because of always 0 idx in slab_debugfs_show().

idx is de-referenced from *v, which points to a loff_t value, with

    unsigned int idx = *(unsigned int *)v;

This will only give the upper 32 bits on big-endian, which remain 0.

Instead of only fixing this de-reference, during discussion it seemed
more appropriate to change the seq_ops so that they use an explicit
iterator in private loc_track struct.

This patch adds idx to loc_track, which will also fix the endianness
bug.

Link: https://lore.kernel.org/r/20211117193932.4049412-1-gerald.schaefer@linux.ibm.com
Link: https://lkml.kernel.org/r/20211126171848.17534-1-gerald.schaefer@linux.ibm.com


Fixes: 64dd6849 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@linux.ibm.com>
Reported-by: default avatarSteffen Maier <maier@linux.ibm.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9ab3b0c8

mm/slub.c

+9 −6
Original line number Diff line number Diff line
@@ -5081,6 +5081,7 @@ struct loc_track { 
	unsigned long max;

	unsigned long count;

	struct location *loc;

	loff_t idx;

};



static struct dentry *slab_debugfs_root;
@@ -6052,11 +6053,11 @@ __initcall(slab_sysfs_init); 
#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS)

static int slab_debugfs_show(struct seq_file *seq, void *v)

{



	struct location *l;

	unsigned int idx = *(unsigned int *)v;

	struct loc_track *t = seq->private;

	struct location *l;

	unsigned long idx;



	idx = (unsigned long) t->idx;

	if (idx < t->count) {

		l = &t->loc[idx];
@@ -6105,16 +6106,18 @@ static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos) 
{

	struct loc_track *t = seq->private;



	v = ppos;

	++*ppos;

	t->idx = ++(*ppos);

	if (*ppos <= t->count)

		return v;

		return ppos;



	return NULL;

}



static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)

{

	struct loc_track *t = seq->private;



	t->idx = *ppos;

	return ppos;

}