From: Johannes Thumshirn <jth@kernel.org>
To: linux-btrfs@vger.kernel.org
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>,
Filipe Manana <fdmanana@kernel.org>,
syzbot+510a1abbb8116eeb341d@syzkaller.appspotmail.com,
Johannes Thumshirn <Johannes.thumshirn@wdc.com>,
Qu Wenruo <wqu@suse.com>
Subject: [PATCH v2] btrfs: fix information leak in btrfs_ioctl_logical_to_ino()
Date: Wed, 17 Apr 2024 15:48:49 +0200 [thread overview]
Message-ID: <7eb2d171cdb1a2a89288a989dc0ef28c21bebc59.1713361686.git.jth@kernel.org> (raw)
From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Syzbot reported the following information leak for in
btrfs_ioctl_logical_to_ino():
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x110 lib/usercopy.c:40
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
_copy_to_user+0xbc/0x110 lib/usercopy.c:40
copy_to_user include/linux/uaccess.h:191 [inline]
btrfs_ioctl_logical_to_ino+0x440/0x750 fs/btrfs/ioctl.c:3499
btrfs_ioctl+0x714/0x1260
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:904 [inline]
__se_sys_ioctl+0x261/0x450 fs/ioctl.c:890
__x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890
x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Uninit was created at:
__kmalloc_large_node+0x231/0x370 mm/slub.c:3921
__do_kmalloc_node mm/slub.c:3954 [inline]
__kmalloc_node+0xb07/0x1060 mm/slub.c:3973
kmalloc_node include/linux/slab.h:648 [inline]
kvmalloc_node+0xc0/0x2d0 mm/util.c:634
kvmalloc include/linux/slab.h:766 [inline]
init_data_container+0x49/0x1e0 fs/btrfs/backref.c:2779
btrfs_ioctl_logical_to_ino+0x17c/0x750 fs/btrfs/ioctl.c:3480
btrfs_ioctl+0x714/0x1260
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:904 [inline]
__se_sys_ioctl+0x261/0x450 fs/ioctl.c:890
__x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890
x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Bytes 40-65535 of 65536 are uninitialized
Memory access of size 65536 starts at ffff888045a40000
This happens, because we're copying a 'struct btrfs_data_container' back
to user-space. This btrfs_data_container is allocated in
'init_data_container()' via kvmalloc(), which does not zero-fill the
memory.
Fix this by using kvzalloc() which zeroes out the memory on allocation.
Reported-by: <syzbot+510a1abbb8116eeb341d@syzkaller.appspotmail.com>
Signed-off-by: Johannes Thumshirn <Johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/backref.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 0bc81b340295..a2de5c05f97c 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -2770,20 +2770,14 @@ struct btrfs_data_container *init_data_container(u32 total_bytes)
size_t alloc_bytes;
alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
- data = kvmalloc(alloc_bytes, GFP_KERNEL);
+ data = kvzalloc(alloc_bytes, GFP_KERNEL);
if (!data)
return ERR_PTR(-ENOMEM);
- if (total_bytes >= sizeof(*data)) {
+ if (total_bytes >= sizeof(*data))
data->bytes_left = total_bytes - sizeof(*data);
- data->bytes_missing = 0;
- } else {
+ else
data->bytes_missing = sizeof(*data) - total_bytes;
- data->bytes_left = 0;
- }
-
- data->elem_cnt = 0;
- data->elem_missed = 0;
return data;
}
--
2.35.3
next reply other threads:[~2024-04-17 13:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-17 13:48 Johannes Thumshirn [this message]
2024-04-17 13:49 ` [PATCH v2] btrfs: fix information leak in btrfs_ioctl_logical_to_ino() Filipe Manana
2024-04-17 21:19 ` David Sterba
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