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    Subject[PATCH 4.9 27/78] fs/dcache.c: fix kmemcheck splat at take_dentry_name_snapshot()
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    [ Upstream commit 6cd00a01f0c1ae6a852b09c59b8dd55cc6c35d1d ]

    Since only dentry->d_name.len + 1 bytes out of DNAME_INLINE_LEN bytes
    are initialized at __d_alloc(), we can't copy the whole size
    unconditionally.

    WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff8fa27465ac50)
    636f6e66696766732e746d70000000000010000000000000020000000188ffff
    i i i i i i i i i i i i i u u u u u u u u u u i i i i i u u u u
    ^
    RIP: 0010:take_dentry_name_snapshot+0x28/0x50
    RSP: 0018:ffffa83000f5bdf8 EFLAGS: 00010246
    RAX: 0000000000000020 RBX: ffff8fa274b20550 RCX: 0000000000000002
    RDX: ffffa83000f5be40 RSI: ffff8fa27465ac50 RDI: ffffa83000f5be60
    RBP: ffffa83000f5bdf8 R08: ffffa83000f5be48 R09: 0000000000000001
    R10: ffff8fa27465ac00 R11: ffff8fa27465acc0 R12: ffff8fa27465ac00
    R13: ffff8fa27465acc0 R14: 0000000000000000 R15: 0000000000000000
    FS: 00007f79737ac8c0(0000) GS:ffffffff8fc30000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffff8fa274c0b000 CR3: 0000000134aa7002 CR4: 00000000000606f0
    take_dentry_name_snapshot+0x28/0x50
    vfs_rename+0x128/0x870
    SyS_rename+0x3b2/0x3d0
    entry_SYSCALL_64_fastpath+0x1a/0xa4
    0xffffffffffffffff

    Link: http://lkml.kernel.org/r/201709131912.GBG39012.QMJLOVFSFFOOtH@I-love.SAKURA.ne.jp
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: Vegard Nossum <vegard.nossum@gmail.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/dcache.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -286,7 +286,8 @@ void take_dentry_name_snapshot(struct na
    spin_unlock(&dentry->d_lock);
    name->name = p->name;
    } else {
    - memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
    + memcpy(name->inline_name, dentry->d_iname,
    + dentry->d_name.len + 1);
    spin_unlock(&dentry->d_lock);
    name->name = name->inline_name;
    }

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