Messages in this thread | | | Date | Tue, 29 Nov 2022 10:23:46 +0800 | Subject | Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac | From | "zhangpeng (AS)" <> |
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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> }
Thanks, Zhang Peng
>> *dst++ = ch > 0xff ? '?' : ch; >> dstlen--; >> } >> -- >> 2.25.1 >> >
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