CVE-2022-50747

In the Linux kernel, the following vulnerability has been resolved:

hfs: Fix OOB Write in hfs_asc2mac

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 in while() before writing to dst

address.