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207764e5d6
syzbot reported a f2fs bug as below:
------------[ cut here ]------------
kernel BUG at fs/f2fs/gc.c:373!
CPU: 0 UID: 0 PID: 5316 Comm: syz.0.0 Not tainted 6.13.0-rc3-syzkaller-00044-gaef25be35d23 #0
RIP: 0010:get_cb_cost fs/f2fs/gc.c:373 [inline]
RIP: 0010:get_gc_cost fs/f2fs/gc.c:406 [inline]
RIP: 0010:f2fs_get_victim+0x68b1/0x6aa0 fs/f2fs/gc.c:912
Call Trace:
<TASK>
__get_victim fs/f2fs/gc.c:1707 [inline]
f2fs_gc+0xc89/0x2f60 fs/f2fs/gc.c:1915
f2fs_ioc_gc fs/f2fs/file.c:2624 [inline]
__f2fs_ioctl+0x4cc9/0xb8b0 fs/f2fs/file.c:4482
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
w/ below testcase, it can reproduce directly:
- dd if=/dev/zero of=/tmp/file bs=1M count=64
- mkfs.f2fs /tmp/file
- mount -t f2fs -o loop,mode=fragment:block /tmp/file /mnt/f2fs
- echo 0 > /sys/fs/f2fs/loop0/min_ssr_sections
- dd if=/dev/zero of=/mnt/f2fs/file bs=1M count=5
- umount /mnt/f2fs
- for((i=4096;i<16384;i+=512)) do inject.f2fs --sit 0 --blk $i --mb mtime --val -1 /tmp/file; done
- mount -o loop /tmp/file /mnt/f2fs
- f2fs_io gc 0 /mnt/f2fs/file
static unsigned int get_cb_cost()
{
...
mtime = f2fs_get_section_mtime(sbi, segno);
f2fs_bug_on(sbi, mtime == INVALID_MTIME);
...
}
The root cause is: mtime in f2fs_sit_entry can be fuzzed to INVALID_MTIME,
then it will trigger BUG_ON in get_cb_cost() during GC.
Let's change behavior of f2fs_get_section_mtime() as below for fix:
- return INVALID_MTIME only if total valid blocks is zero.
- return INVALID_MTIME - 1 if average mtime calculated is
INVALID_MTIME.
Fixes:
|
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
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the problems which may result by upgrading your kernel.