High · published December 9, 2025
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to do sanity check on direct node in truncate_dnode()
syzbot reports below bug:
BUG: KASAN: slab-use-after-free in f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
Read of size 4 at addr ffff88802a25c000 by task syz-executor148/5000
CPU: 1 PID: 5000 Comm: syz-executor148 Not tainted 6.4.0-rc7-syzkaller-00041-ge660abd551f1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
print_report mm/kasan/report.c:462 [inline]
kasan_report+0x11c/0x130 mm/kasan/report.c:572
f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
truncate_dnode+0x229/0x2e0 fs/f2fs/node.c:944
f2fs_truncate_inode_blocks+0x64b/0xde0 fs/f2fs/node.c:1154
f2fs_do_truncate_blocks+0x4ac/0xf30 fs/f2fs/file.c:721
f2fs_truncate_blocks+0x7b/0x300 fs/f2fs/file.c:749
f2fs_truncate.part.0+0x4a5/0x630 fs/f2fs/file.c:799
f2fs_truncate include/linux/fs.h:825 [inline]
f2fs_setattr+0x1738/0x2090 fs/f2fs/file.c:1006
notify_change+0xb2c/0x1180 fs/attr.c:483
do_truncate+0x143/0x200 fs/open.c:66
handle_truncate fs/namei.c:3295 [inline]
do_open fs/namei.c:3640 [inline]
path_openat+0x2083/0x2750 fs/namei.c:3791
do_filp_open+0x1ba/0x410 fs/namei.c:3818
do_sys_openat2+0x16d/0x4c0 fs/open.c:1356
do_sys_open fs/open.c:1372 [inline]
__do_sys_creat fs/open.c:1448 [inline]
__se_sys_creat fs/open.c:1442 [inline]
__x64_sys_creat+0xcd/0x120 fs/open.c:1442
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The root cause is, inodeA references inodeB via inodeB's ino, once inodeA
is truncated, it calls truncate_dnode() to truncate data blocks in inodeB's
node page, it traverse mapping data from node->i.i_addr[0] to
node->i.i_addr[ADDRS_PER_BLOCK() - 1], result in out-of-boundary access.
This patch fixes to add sanity check on dnode page in truncate_dnode(),
so that, it can help to avoid triggering such issue, and once it encounters
such issue, it will record newly introduced ERROR_INVALID_NODE_REFERENCE
error into superblock, later fsck can detect such issue and try repairing.
Also, it removes f2fs_truncate_data_blocks() for cleanup due to the
function has only one caller, and uses f2fs_truncate_data_blocks_range()
instead.