diff mbox series

[v2] btrfs: fix information leak in btrfs_ioctl_logical_to_ino()

Message ID 7eb2d171cdb1a2a89288a989dc0ef28c21bebc59.1713361686.git.jth@kernel.org (mailing list archive)
State New
Headers show
Series [v2] btrfs: fix information leak in btrfs_ioctl_logical_to_ino() | expand

Commit Message

Johannes Thumshirn April 17, 2024, 1:48 p.m. UTC 
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(-)

Comments

Filipe Manana April 17, 2024, 1:49 p.m. UTC | #1 
On Wed, Apr 17, 2024 at 2:49 PM Johannes Thumshirn <jth@kernel.org> wrote:
>
> 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>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good, thanks.

> ---
>  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
>
David Sterba April 17, 2024, 9:19 p.m. UTC | #2 
On Wed, Apr 17, 2024 at 03:48:49PM +0200, Johannes Thumshirn wrote:
> 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>

Reviewed-by: David Sterba <dsterba@suse.com>
diff mbox series

Patch

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;
 }