[SRU][N][PATCH 2/2] f2fs: fix to don't panic system for no free segment fault injection

[Massimiliano Pellizzer]

From: Chao Yu <chao at kernel.org>

f2fs: fix to don't panic system for no free segment fault injection

syzbot reports a f2fs bug as below:

F2FS-fs (loop0): inject no free segment in get_new_segment of __allocate_new_segment+0x1ce/0x940 fs/f2fs/segment.c:3167
F2FS-fs (loop0): Stopped filesystem due to reason: 7
------------[ cut here ]------------
kernel BUG at fs/f2fs/segment.c:2748!
CPU: 0 UID: 0 PID: 5109 Comm: syz-executor304 Not tainted 6.11.0-rc6-syzkaller-00363-g89f5e14d05b4 #0
RIP: 0010:get_new_segment fs/f2fs/segment.c:2748 [inline]
RIP: 0010:new_curseg+0x1f61/0x1f70 fs/f2fs/segment.c:2836
Call Trace:
 __allocate_new_segment+0x1ce/0x940 fs/f2fs/segment.c:3167
 f2fs_allocate_new_section fs/f2fs/segment.c:3181 [inline]
 f2fs_allocate_pinning_section+0xfa/0x4e0 fs/f2fs/segment.c:3195
 f2fs_expand_inode_data+0x5d6/0xbb0 fs/f2fs/file.c:1799
 f2fs_fallocate+0x448/0x960 fs/f2fs/file.c:1903
 vfs_fallocate+0x553/0x6c0 fs/open.c:334
 do_vfs_ioctl+0x2592/0x2e50 fs/ioctl.c:886
 __do_sys_ioctl fs/ioctl.c:905 [inline]
 __se_sys_ioctl+0x81/0x170 fs/ioctl.c:893
 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
RIP: 0010:get_new_segment fs/f2fs/segment.c:2748 [inline]
RIP: 0010:new_curseg+0x1f61/0x1f70 fs/f2fs/segment.c:2836

The root cause is when we inject no free segment fault into f2fs,
we should not panic system, fix it.

Fixes: 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT")
Reported-by: syzbot+341e5f32ebafbb46b81c at syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/000000000000f0ee5b0621ab694b@google.com
Signed-off-by: Chao Yu <chao at kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk at kernel.org>
(backported from commit 65a6ce4726c27b45600303f06496fef46d00b57f)
[mpellizzer: context adjusted due to missing commit:
- 1081b5121b27 f2fs: clean up new_curseg()]
CVE-2024-49887
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 fs/f2fs/segment.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 70a3b66011bf..63538f016192 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2717,6 +2717,7 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
 								MAIN_SECS(sbi));
 		if (secno >= MAIN_SECS(sbi)) {
 			ret = -ENOSPC;
+			f2fs_bug_on(sbi, 1);
 			goto out_unlock;
 		}
 	}
@@ -2727,6 +2728,7 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
 							MAIN_SECS(sbi));
 		if (secno >= MAIN_SECS(sbi)) {
 			ret = -ENOSPC;
+			f2fs_bug_on(sbi, 1);
 			goto out_unlock;
 		}
 	}
@@ -2761,10 +2763,8 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
 out_unlock:
 	spin_unlock(&free_i->segmap_lock);
 
-	if (ret) {
+	if (ret)
 		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_NO_SEGMENT);
-		f2fs_bug_on(sbi, 1);
-	}
 	return ret;
 }
 
-- 
2.43.0