linux-kernel - [PATCH] exfat: Avoid allocating upcase table using kcalloc()

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Message-Id: <20201124194749.4041176-1-123321artyom@gmail.com>
Date:   Tue, 24 Nov 2020 22:47:49 +0300
From:   Artem Labazov <123321artyom@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     123321artyom@...il.com, stable@...r.kernel.org,
        Namjae Jeon <namjae.jeon@...sung.com>,
        Sungjong Seo <sj1557.seo@...sung.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] exfat: Avoid allocating upcase table using kcalloc()

The table for Unicode upcase conversion requires an order-5 allocation,
which may fail on a highly-fragmented system:

 pool-udisksd: page allocation failure: order:5, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 4 PID: 3756880 Comm: pool-udisksd Tainted: G     U            5.8.10-200.fc32.x86_64 #1
 Hardware name: Dell Inc. XPS 13 9360/0PVG6D, BIOS 2.13.0 11/14/2019
 Call Trace:
  dump_stack+0x6b/0x88
  warn_alloc.cold+0x75/0xd9
  ? _cond_resched+0x16/0x40
  ? __alloc_pages_direct_compact+0x144/0x150
  __alloc_pages_slowpath.constprop.0+0xcfa/0xd30
  ? __schedule+0x28a/0x840
  ? __wait_on_bit_lock+0x92/0xa0
  __alloc_pages_nodemask+0x2df/0x320
  kmalloc_order+0x1b/0x80
  kmalloc_order_trace+0x1d/0xa0
  exfat_create_upcase_table+0x115/0x390 [exfat]
  exfat_fill_super+0x3ef/0x7f0 [exfat]
  ? sget_fc+0x1d0/0x240
  ? exfat_init_fs_context+0x120/0x120 [exfat]
  get_tree_bdev+0x15c/0x250
  vfs_get_tree+0x25/0xb0
  do_mount+0x7c3/0xaf0
  ? copy_mount_options+0xab/0x180
  __x64_sys_mount+0x8e/0xd0
  do_syscall_64+0x4d/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Make the driver use vmalloc() to eliminate the issue.

Cc: stable@...r.kernel.org # v5.7+
Signed-off-by: Artem Labazov <123321artyom@...il.com>
---
 fs/exfat/nls.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c
index 675d0e7058c5..0582faf8de77 100644
--- a/fs/exfat/nls.c
+++ b/fs/exfat/nls.c
@@ -6,6 +6,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/buffer_head.h>
+#include <linux/vmalloc.h>
 #include <asm/unaligned.h>

 #include "exfat_raw.h"
@@ -659,7 +660,7 @@ static int exfat_load_upcase_table(struct super_block *sb,
 	unsigned char skip = false;
 	unsigned short *upcase_table;

-	upcase_table = kcalloc(UTBL_COUNT, sizeof(unsigned short), GFP_KERNEL);
+	upcase_table = vmalloc(UTBL_COUNT*sizeof(unsigned short));
 	if (!upcase_table)
 		return -ENOMEM;

@@ -715,7 +716,7 @@ static int exfat_load_default_upcase_table(struct super_block *sb)
 	unsigned short uni = 0, *upcase_table;
 	unsigned int index = 0;

-	upcase_table = kcalloc(UTBL_COUNT, sizeof(unsigned short), GFP_KERNEL);
+	upcase_table = vmalloc(UTBL_COUNT*sizeof(unsigned short));
 	if (!upcase_table)
 		return -ENOMEM;

@@ -803,5 +804,5 @@ int exfat_create_upcase_table(struct super_block *sb)

 void exfat_free_upcase_table(struct exfat_sb_info *sbi)
 {
-	kfree(sbi->vol_utbl);
+	vfree(sbi->vol_utbl);
 }
-- 
2.26.2