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    Subject[PATCH 4.19 059/191] f2fs: fix uninit-value in f2fs_lookup
    Date
    From: Chao Yu <yuchao0@huawei.com>

    [ Upstream commit 6d7ab88a98c1b7a47c228f8ffb4f44d631eaf284 ]

    As syzbot reported:

    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x21c/0x280 lib/dump_stack.c:118
    kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:122
    __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:219
    f2fs_lookup+0xe05/0x1a80 fs/f2fs/namei.c:503
    lookup_open fs/namei.c:3082 [inline]
    open_last_lookups fs/namei.c:3177 [inline]
    path_openat+0x2729/0x6a90 fs/namei.c:3365
    do_filp_open+0x2b8/0x710 fs/namei.c:3395
    do_sys_openat2+0xa88/0x1140 fs/open.c:1168
    do_sys_open fs/open.c:1184 [inline]
    __do_compat_sys_openat fs/open.c:1242 [inline]
    __se_compat_sys_openat+0x2a4/0x310 fs/open.c:1240
    __ia32_compat_sys_openat+0x56/0x70 fs/open.c:1240
    do_syscall_32_irqs_on arch/x86/entry/common.c:80 [inline]
    __do_fast_syscall_32+0x129/0x180 arch/x86/entry/common.c:139
    do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:162
    do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:205
    entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

    In f2fs_lookup(), @res_page could be used before being initialized,
    because in __f2fs_find_entry(), once F2FS_I(dir)->i_current_depth was
    been fuzzed to zero, then @res_page will never be initialized, causing
    this kmsan warning, relocating @res_page initialization place to fix
    this bug.

    Reported-by: syzbot+0eac6f0bbd558fd866d7@syzkaller.appspotmail.com
    Signed-off-by: Chao Yu <yuchao0@huawei.com>
    Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/f2fs/dir.c | 8 +++-----
    1 file changed, 3 insertions(+), 5 deletions(-)

    diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
    index ebe19894884be..2cd85ce3e4502 100644
    --- a/fs/f2fs/dir.c
    +++ b/fs/f2fs/dir.c
    @@ -208,16 +208,15 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
    unsigned int max_depth;
    unsigned int level;

    + *res_page = NULL;
    +
    if (f2fs_has_inline_dentry(dir)) {
    - *res_page = NULL;
    de = f2fs_find_in_inline_dir(dir, fname, res_page);
    goto out;
    }

    - if (npages == 0) {
    - *res_page = NULL;
    + if (npages == 0)
    goto out;
    - }

    max_depth = F2FS_I(dir)->i_current_depth;
    if (unlikely(max_depth > MAX_DIR_HASH_DEPTH)) {
    @@ -229,7 +228,6 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
    }

    for (level = 0; level < max_depth; level++) {
    - *res_page = NULL;
    de = find_in_level(dir, level, fname, res_page);
    if (de || IS_ERR(*res_page))
    break;
    --
    2.27.0


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