Re: [PATCH] f2fs: file: add checks to f2fs_ioc_flush_device()

From: Chao Yu
Date: Mon Aug 12 2024 - 23:50:38 EST


On 2024/8/1 15:17, Roman Smirnov wrote:
If invalid data is copied from user space and if GET_SEGNO()
returns NULL_SEGNO an overflow is possible.

Can you explain in which condition that FDEV(range.dev_num).start_blk or
FDEV(range.dev_num).end_blk will be invalid?

> > Add checks for invalid values.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
---
fs/f2fs/file.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 168f08507004..1b9c4fee9db1 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3093,6 +3093,9 @@ static int f2fs_ioc_flush_device(struct file *filp, unsigned long arg)
start_segno = dev_start_segno;
end_segno = min(start_segno + range.segments, dev_end_segno);
+ if (start_segno > F2FS_MAX_SEGMENT - range.segments || end_segno == NULL_SEGNO)
+ return -EINVAL;

It missed to call mnt_drop_write_file() before return.

Thanks,

+
while (start_segno < end_segno) {
if (!f2fs_down_write_trylock(&sbi->gc_lock)) {
ret = -EBUSY;