From bf9fb25f3265605572f04e5c7836bb83ee345236 Mon Sep 17 00:00:00 2001 From: Chao Yu Date: Fri, 30 Dec 2022 23:43:32 +0800 Subject: [PATCH] f2fs: fix to avoid NULL pointer dereference in f2fs_issue_flush() commit b3d83066cbebc76dbac8a5fca931f64b4c6fff34 upstream. With below two cases, it will cause NULL pointer dereference when accessing SM_I(sbi)->fcc_info in f2fs_issue_flush(). a) If kthread_run() fails in f2fs_create_flush_cmd_control(), it will release SM_I(sbi)->fcc_info, - mount -o noflush_merge /dev/vda /mnt/f2fs - mount -o remount,flush_merge /dev/vda /mnt/f2fs -- kthread_run() fails - dd if=/dev/zero of=/mnt/f2fs/file bs=4k count=1 conv=fsync b) we will never allocate memory for SM_I(sbi)->fcc_info w/ below testcase, - mount -o ro /dev/vda /mnt/f2fs - mount -o rw,remount /dev/vda /mnt/f2fs - dd if=/dev/zero of=/mnt/f2fs/file bs=4k count=1 conv=fsync In order to fix this issue, let change as below: - fix error path handling in f2fs_create_flush_cmd_control(). - allocate SM_I(sbi)->fcc_info even if readonly is on. Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim --- fs/f2fs/segment.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -665,9 +665,7 @@ init_thread: "f2fs_flush-%u:%u", MAJOR(dev), MINOR(dev)); if (IS_ERR(fcc->f2fs_issue_flush)) { err = PTR_ERR(fcc->f2fs_issue_flush); - kfree(fcc); - SM_I(sbi)->fcc_info = NULL; - return err; + fcc->f2fs_issue_flush = NULL; } return err; @@ -5064,11 +5062,9 @@ int f2fs_build_segment_manager(struct f2 init_f2fs_rwsem(&sm_info->curseg_lock); - if (!f2fs_readonly(sbi->sb)) { - err = f2fs_create_flush_cmd_control(sbi); - if (err) - return err; - } + err = f2fs_create_flush_cmd_control(sbi); + if (err) + return err; err = create_discard_cmd_control(sbi); if (err)