Messages in this thread | | | Date | Thu, 1 Dec 2022 09:53:48 +0800 | Subject | Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac | From | "zhangpeng (AS)" <> |
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On 2022/11/30 3:08, Viacheslav Dubeyko wrote: >> On Nov 28, 2022, at 6:23 PM, zhangpeng (AS) <zhangpeng362@huawei.com> wrote: >> >> On 2022/11/29 3:29, Viacheslav Dubeyko wrote: >>>> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote: >>>> >>>> From: ZhangPeng <zhangpeng362@huawei.com> >>>> >>>> Syzbot reported a OOB Write bug: >>>> >>>> loop0: detected capacity change from 0 to 64 >>>> ================================================================== >>>> BUG: KASAN: slab-out-of-bounds in hfs_asc2mac+0x467/0x9a0 >>>> fs/hfs/trans.c:133 >>>> Write of size 1 at addr ffff88801848314e by task syz-executor391/3632 >>>> >>>> Call Trace: >>>> <TASK> >>>> __dump_stack lib/dump_stack.c:88 [inline] >>>> dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106 >>>> print_address_description+0x74/0x340 mm/kasan/report.c:284 >>>> print_report+0x107/0x1f0 mm/kasan/report.c:395 >>>> kasan_report+0xcd/0x100 mm/kasan/report.c:495 >>>> hfs_asc2mac+0x467/0x9a0 fs/hfs/trans.c:133 >>>> hfs_cat_build_key+0x92/0x170 fs/hfs/catalog.c:28 >>>> hfs_lookup+0x1ab/0x2c0 fs/hfs/dir.c:31 >>>> lookup_open fs/namei.c:3391 [inline] >>>> open_last_lookups fs/namei.c:3481 [inline] >>>> path_openat+0x10e6/0x2df0 fs/namei.c:3710 >>>> do_filp_open+0x264/0x4f0 fs/namei.c:3740 >>>> >>>> If in->len is much larger than HFS_NAMELEN(31) which is the maximum >>>> length of an HFS filename, a OOB Write could occur in hfs_asc2mac(). In >>>> that case, when the dst reaches the boundary, the srclen is still >>>> greater than 0, which causes a OOB Write. >>>> Fix this by adding a Check on dstlen before Writing to dst address. >>>> >>>> Fixes: 328b92278650 ("[PATCH] hfs: NLS support") >>>> Reported-by: syzbot+dc3b1cf9111ab5fe98e7@syzkaller.appspotmail.com >>>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com> >>>> --- >>>> fs/hfs/trans.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/fs/hfs/trans.c b/fs/hfs/trans.c >>>> index 39f5e343bf4d..886158db07b3 100644 >>>> --- a/fs/hfs/trans.c >>>> +++ b/fs/hfs/trans.c >>>> @@ -130,6 +130,8 @@ void hfs_asc2mac(struct super_block *sb, struct hfs_name *out, const struct qstr >>>> dst += size; >>>> dstlen -= size; >>>> } else { >>>> + if (dstlen == 0) >>>> + goto out; >>> Maybe, it makes sense to use dstlen instead of srclen in while()? >>> >>> We have now: >>> >>> while (srclen > 0) { >>> <skipped> >>> } else { >>> <skipped> >>> } >>> >>> We can use instead: >>> >>> while (dstlen > 0) { >>> <skipped> >>> } else { >>> <skipped> >>> } >>> >>> Will it fix the issue? >>> >>> Thanks, >>> Slava. >> Thank you for your help. >> >> After testing, it fix the issue. >> Would it be better to add dstlen > 0 instead of replacing srclen > 0 with dstlen > 0? >> Because there may be dstlen > 0 and srclen <= 0. >> >> we can use: >> >> while (srclen > 0 && dstlen > 0) { >> <skipped> >> } else { >> <skipped> >> } >> > Looks good to me.
Can I put you down as a Reviewed-by or Suggested-by?
Thanks, Zhang Peng
> Thanks, > Slava. > >> Thanks, >> Zhang Peng >> >>>> *dst++ = ch > 0xff ? '?' : ch; >>>> dstlen--; >>>> } >>>> -- >>>> 2.25.1
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