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    Subject[PATCH v2 1/7] pipe, sysctl: drop 'min' parameter from pipe-max-size converter
    Date
    From: Eric Biggers <ebiggers@google.com>

    Before validating the given value against pipe_min_size,
    do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
    value up to pipe_min_size. Therefore, the second check against
    pipe_min_size is redundant. Remove it.

    Acked-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    ---
    fs/pipe.c | 10 +++-------
    include/linux/pipe_fs_i.h | 2 +-
    kernel/sysctl.c | 15 +--------------
    3 files changed, 5 insertions(+), 22 deletions(-)

    diff --git a/fs/pipe.c b/fs/pipe.c
    index 6d98566201ef..a75f5d2ca99c 100644
    --- a/fs/pipe.c
    +++ b/fs/pipe.c
    @@ -35,11 +35,6 @@
    */
    unsigned int pipe_max_size = 1048576;

    -/*
    - * Minimum pipe size, as required by POSIX
    - */
    -unsigned int pipe_min_size = PAGE_SIZE;
    -
    /* Maximum allocatable pages per user. Hard limit is unset by default, soft
    * matches default values.
    */
    @@ -1024,8 +1019,9 @@ unsigned int round_pipe_size(unsigned int size)
    {
    unsigned long nr_pages;

    - if (size < pipe_min_size)
    - size = pipe_min_size;
    + /* Minimum pipe size, as required by POSIX */
    + if (size < PAGE_SIZE)
    + size = PAGE_SIZE;

    nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
    if (nr_pages == 0)
    diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
    index 2dc5e9870fcd..7d9beda14584 100644
    --- a/include/linux/pipe_fs_i.h
    +++ b/include/linux/pipe_fs_i.h
    @@ -167,7 +167,7 @@ void pipe_lock(struct pipe_inode_info *);
    void pipe_unlock(struct pipe_inode_info *);
    void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);

    -extern unsigned int pipe_max_size, pipe_min_size;
    +extern unsigned int pipe_max_size;
    extern unsigned long pipe_user_pages_hard;
    extern unsigned long pipe_user_pages_soft;
    int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
    diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    index 557d46728577..a71ebb5c5182 100644
    --- a/kernel/sysctl.c
    +++ b/kernel/sysctl.c
    @@ -1820,7 +1820,6 @@ static struct ctl_table fs_table[] = {
    .maxlen = sizeof(pipe_max_size),
    .mode = 0644,
    .proc_handler = &pipe_proc_fn,
    - .extra1 = &pipe_min_size,
    },
    {
    .procname = "pipe-user-pages-hard",
    @@ -2622,16 +2621,10 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
    do_proc_douintvec_minmax_conv, &param);
    }

    -struct do_proc_dopipe_max_size_conv_param {
    - unsigned int *min;
    -};
    -
    static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
    unsigned int *valp,
    int write, void *data)
    {
    - struct do_proc_dopipe_max_size_conv_param *param = data;
    -
    if (write) {
    unsigned int val;

    @@ -2642,9 +2635,6 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
    if (val == 0)
    return -EINVAL;

    - if (param->min && *param->min > val)
    - return -ERANGE;
    -
    *valp = val;
    } else {
    unsigned int val = *valp;
    @@ -2657,11 +2647,8 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
    int proc_dopipe_max_size(struct ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
    {
    - struct do_proc_dopipe_max_size_conv_param param = {
    - .min = (unsigned int *) table->extra1,
    - };
    return do_proc_douintvec(table, write, buffer, lenp, ppos,
    - do_proc_dopipe_max_size_conv, &param);
    + do_proc_dopipe_max_size_conv, NULL);
    }

    static void validate_coredump_safety(void)
    --
    2.15.1
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