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    Subject[PATCH 5.10 626/717] ubifs: wbuf: Dont leak kernel memory to flash
    Date
    From: Richard Weinberger <richard@nod.at>

    commit 20f1431160c6b590cdc269a846fc5a448abf5b98 upstream.

    Write buffers use a kmalloc()'ed buffer, they can leak
    up to seven bytes of kernel memory to flash if writes are not
    aligned.
    So use ubifs_pad() to fill these gaps with padding bytes.
    This was never a problem while scanning because the scanner logic
    manually aligns node lengths and skips over these gaps.

    Cc: <stable@vger.kernel.org>
    Fixes: 1e51764a3c2ac05a2 ("UBIFS: add new flash file system")
    Signed-off-by: Richard Weinberger <richard@nod.at>
    Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
    Signed-off-by: Richard Weinberger <richard@nod.at>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ubifs/io.c | 13 +++++++++++--
    1 file changed, 11 insertions(+), 2 deletions(-)

    --- a/fs/ubifs/io.c
    +++ b/fs/ubifs/io.c
    @@ -319,7 +319,7 @@ void ubifs_pad(const struct ubifs_info *
    {
    uint32_t crc;

    - ubifs_assert(c, pad >= 0 && !(pad & 7));
    + ubifs_assert(c, pad >= 0);

    if (pad >= UBIFS_PAD_NODE_SZ) {
    struct ubifs_ch *ch = buf;
    @@ -764,6 +764,10 @@ int ubifs_wbuf_write_nolock(struct ubifs
    * write-buffer.
    */
    memcpy(wbuf->buf + wbuf->used, buf, len);
    + if (aligned_len > len) {
    + ubifs_assert(c, aligned_len - len < 8);
    + ubifs_pad(c, wbuf->buf + wbuf->used + len, aligned_len - len);
    + }

    if (aligned_len == wbuf->avail) {
    dbg_io("flush jhead %s wbuf to LEB %d:%d",
    @@ -856,13 +860,18 @@ int ubifs_wbuf_write_nolock(struct ubifs
    }

    spin_lock(&wbuf->lock);
    - if (aligned_len)
    + if (aligned_len) {
    /*
    * And now we have what's left and what does not take whole
    * max. write unit, so write it to the write-buffer and we are
    * done.
    */
    memcpy(wbuf->buf, buf + written, len);
    + if (aligned_len > len) {
    + ubifs_assert(c, aligned_len - len < 8);
    + ubifs_pad(c, wbuf->buf + len, aligned_len - len);
    + }
    + }

    if (c->leb_size - wbuf->offs >= c->max_write_size)
    wbuf->size = c->max_write_size;

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