linux-kernel - [PATCH v4] tools/mm: Fix slabinfo crash when MAX

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Message-ID: <20241031105534.565533-1-marc.c.dionne@gmail.com>
Date: Thu, 31 Oct 2024 07:55:34 -0300
From: Marc Dionne <marc.c.dionne@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Vlastimil Babka <vbabka@...e.cz>,
	Marc Dionne <marc.dionne@...istor.com>
Subject: [PATCH v4] tools/mm: Fix slabinfo crash when MAX_SLABS is exceeded

From: Marc Dionne <marc.dionne@...istor.com>

The number of slabs can easily exceed the hard coded MAX_SLABS in the
slabinfo tool, causing it to overwrite memory and crash.

Increase the value of MAX_SLABS, and check if that has been exceeded for
each new slab, instead of at the end when it's already too late.  Also
move the check for MAX_ALIASES into the loop body.

Signed-off-by: Marc Dionne <marc.dionne@...istor.com>
---
 tools/mm/slabinfo.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/mm/slabinfo.c b/tools/mm/slabinfo.c
index cfaeaea71042..1a9b807a48c3 100644
--- a/tools/mm/slabinfo.c
+++ b/tools/mm/slabinfo.c
@@ -21,7 +21,7 @@
 #include <regex.h>
 #include <errno.h>
 
-#define MAX_SLABS 500
+#define MAX_SLABS 2000
 #define MAX_ALIASES 500
 #define MAX_NODES 1024
 
@@ -1228,6 +1228,8 @@ static void read_slab_dir(void)
 				continue;
 		switch (de->d_type) {
 		   case DT_LNK:
+			if (alias - aliasinfo == MAX_ALIASES)
+				fatal("Too many aliases\n");
 			alias->name = strdup(de->d_name);
 			count = readlink(de->d_name, buffer, sizeof(buffer)-1);
 
@@ -1242,6 +1244,8 @@ static void read_slab_dir(void)
 			alias++;
 			break;
 		   case DT_DIR:
+			if (slab - slabinfo == MAX_SLABS)
+				fatal("Too many slabs\n");
 			if (chdir(de->d_name))
 				fatal("Unable to access slab %s\n", slab->name);
 			slab->name = strdup(de->d_name);
@@ -1310,10 +1314,6 @@ static void read_slab_dir(void)
 	slabs = slab - slabinfo;
 	actual_slabs = slabs;
 	aliases = alias - aliasinfo;
-	if (slabs > MAX_SLABS)
-		fatal("Too many slabs\n");
-	if (aliases > MAX_ALIASES)
-		fatal("Too many aliases\n");
 }
 
 static void output_slabs(void)
-- 
2.47.0