RE: [PATCH v3] exfat: Avoid allocating upcase table using kcalloc()

[Sungjong Seo]

> 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
> 
> Convert kcalloc/kfree to their kv* variants to eliminate the issue.
> 
> Cc: stable@xxxxxxxxxxxxxxx # v5.7+
> Signed-off-by: Artem Labazov <123321artyom@xxxxxxxxx>

Looks good.
Thanks for your contribution.

Reviewed-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>

> ---
> v2: replace vmalloc with vzalloc to avoid uninitialized memory access
> v3: use kv* functions to attempt kmalloc first
> 
>  fs/exfat/nls.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c index
> 675d0e7058c5..314d5407a1be 100644
> --- a/fs/exfat/nls.c
> +++ b/fs/exfat/nls.c
> @@ -659,7 +659,7 @@ 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 = kvcalloc(UTBL_COUNT, sizeof(unsigned short),
> +GFP_KERNEL);
>  	if (!upcase_table)
>  		return -ENOMEM;
> 
> @@ -715,7 +715,7 @@ 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 = kvcalloc(UTBL_COUNT, sizeof(unsigned short),
> +GFP_KERNEL);
>  	if (!upcase_table)
>  		return -ENOMEM;
> 
> @@ -803,5 +803,5 @@ int exfat_create_upcase_table(struct super_block *sb)
> 
>  void exfat_free_upcase_table(struct exfat_sb_info *sbi)  {
> -	kfree(sbi->vol_utbl);
> +	kvfree(sbi->vol_utbl);
>  }
> --
> 2.26.2