6.8-stable review patch. If anyone has any objections, please let me know.
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From: Johannes Thumshirn johannes.thumshirn@wdc.com
commit 2f7ef5bb4a2f3e481ef05fab946edb97c84f67cf upstream.
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.
CC: stable@vger.kernel.org # 4.14+ Reported-by: syzbot+510a1abbb8116eeb341d@syzkaller.appspotmail.com Reviewed-by: Qu Wenruo wqu@suse.com Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Johannes Thumshirn Johannes.thumshirn@wdc.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/backref.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-)
--- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -2773,20 +2773,14 @@ struct btrfs_data_container *init_data_c 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; }