lkml.org 
[lkml]   [2022]   [Apr]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] exfat: check if cluster num is valid
2022-04-19 2:39 GMT+09:00, Tadeusz Struk <tadeusz.struk@linaro.org>:
Hi Tadeusz,

> Syzbot reported slab-out-of-bounds read in exfat_clear_bitmap.
> This was triggered by reproducer calling truncate with size 0,
> which causes the following trace:
>
> BUG: KASAN: slab-out-of-bounds in exfat_clear_bitmap+0x147/0x490
> fs/exfat/balloc.c:174
> Read of size 8 at addr ffff888115aa9508 by task syz-executor251/365
>
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack_lvl+0x1e2/0x24b lib/dump_stack.c:118
> print_address_description+0x81/0x3c0 mm/kasan/report.c:233
> __kasan_report mm/kasan/report.c:419 [inline]
> kasan_report+0x1a4/0x1f0 mm/kasan/report.c:436
> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
> exfat_clear_bitmap+0x147/0x490 fs/exfat/balloc.c:174
> exfat_free_cluster+0x25a/0x4a0 fs/exfat/fatent.c:181
> __exfat_truncate+0x99e/0xe00 fs/exfat/file.c:217
> exfat_truncate+0x11b/0x4f0 fs/exfat/file.c:243
> exfat_setattr+0xa03/0xd40 fs/exfat/file.c:339
> notify_change+0xb76/0xe10 fs/attr.c:336
> do_truncate+0x1ea/0x2d0 fs/open.c:65
Could you please share how to reproduce this ?

Thanks.
>
> Add checks to validate if cluster number is within valid range in
> exfat_clear_bitmap() and exfat_set_bitmap()
>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Sungjong Seo <sj1557.seo@samsung.com>
> Cc: linux-fsdevel@vger.kernel.org
> Cc: stable@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
>
> Link:
> https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
> Reported-by: syzbot+a4087e40b9c13aad7892@syzkaller.appspotmail.com
> Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
> Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
> ---
> fs/exfat/balloc.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
> index 03f142307174..4ed81f86f993 100644
> --- a/fs/exfat/balloc.c
> +++ b/fs/exfat/balloc.c
> @@ -149,6 +149,9 @@ int exfat_set_bitmap(struct inode *inode, unsigned int
> clu, bool sync)
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
>
> WARN_ON(clu < EXFAT_FIRST_CLUSTER);
> + if (clu > EXFAT_DATA_CLUSTER_COUNT(sbi))
> + return -EINVAL;
> +
> ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
> i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
> b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
> @@ -167,6 +170,9 @@ void exfat_clear_bitmap(struct inode *inode, unsigned
> int clu, bool sync)
> struct exfat_mount_options *opts = &sbi->options;
>
> WARN_ON(clu < EXFAT_FIRST_CLUSTER);
> + if (clu > EXFAT_DATA_CLUSTER_COUNT(sbi))
> + return;
> +
> ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
> i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
> b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
> --
> 2.35.1
>
>

\
 
 \ /
  Last update: 2022-04-22 07:56    [W:0.153 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site