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    Subject[PATCH AUTOSEL 4.19 040/206] kernel/sys.c: avoid copying possible padding bytes in copy_to_user
    Date
    From: Joe Perches <joe@perches.com>

    [ Upstream commit 5e1aada08cd19ea652b2d32a250501d09b02ff2e ]

    Initialization is not guaranteed to zero padding bytes so use an
    explicit memset instead to avoid leaking any kernel content in any
    possible padding bytes.

    Link: http://lkml.kernel.org/r/dfa331c00881d61c8ee51577a082d8bebd61805c.camel@perches.com
    Signed-off-by: Joe Perches <joe@perches.com>
    Cc: Dan Carpenter <error27@gmail.com>
    Cc: Julia Lawall <julia.lawall@lip6.fr>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Kees Cook <keescook@chromium.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/sys.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/kernel/sys.c b/kernel/sys.c
    index 096932a450466..baf60a3aa34b7 100644
    --- a/kernel/sys.c
    +++ b/kernel/sys.c
    @@ -1275,11 +1275,13 @@ SYSCALL_DEFINE1(uname, struct old_utsname __user *, name)

    SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
    {
    - struct oldold_utsname tmp = {};
    + struct oldold_utsname tmp;

    if (!name)
    return -EFAULT;

    + memset(&tmp, 0, sizeof(tmp));
    +
    down_read(&uts_sem);
    memcpy(&tmp.sysname, &utsname()->sysname, __OLD_UTS_LEN);
    memcpy(&tmp.nodename, &utsname()->nodename, __OLD_UTS_LEN);
    --
    2.25.1
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