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    Subject[RFC][PATCH 1/4] anon_inode fcntl() checks: report failure for fcntl(F_SETFL) on signalfd
    Date
    anon_inode interfaces often do not support flags that can be set
    by fcntl(). Right now using fcntl() to set these flags falsely
    reports success for things like O_ASYNC (yet SIGIO is not delivered).

    Report failure when userspace attempts to set unsupported flags
    on signalfd files with fcntl().

    Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
    Cc: Davide Libenzi <davidel@xmailserver.org>
    ---
    fs/signalfd.c | 19 +++++++++++++------
    1 files changed, 13 insertions(+), 6 deletions(-)

    diff --git a/fs/signalfd.c b/fs/signalfd.c
    index 1dabe4e..3016f3b 100644
    --- a/fs/signalfd.c
    +++ b/fs/signalfd.c
    @@ -199,7 +199,19 @@ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
    return total ? total: ret;
    }

    +static int signalfd_check_flags(int flags)
    +{
    + /* Check the SFD_* constants for consistency. */
    + BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
    + BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
    +
    + if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
    + return -EINVAL;
    + return 0;
    +}
    +
    static const struct file_operations signalfd_fops = {
    + .check_flags = signalfd_check_flags,
    .release = signalfd_release,
    .poll = signalfd_poll,
    .read = signalfd_read,
    @@ -211,13 +223,8 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
    sigset_t sigmask;
    struct signalfd_ctx *ctx;

    - /* Check the SFD_* constants for consistency. */
    - BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
    - BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
    -
    - if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
    + if (signalfd_check_flags(flags))
    return -EINVAL;
    -
    if (sizemask != sizeof(sigset_t) ||
    copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
    return -EINVAL;
    --
    1.6.3.3


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