lkml.org 
[lkml]   [2019]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.14 03/71] mm/usercopy: use memory range to be accessed for wraparound check
    Date
    From: Isaac J. Manjarres <isaacm@codeaurora.org>

    commit 951531691c4bcaa59f56a316e018bc2ff1ddf855 upstream.

    Currently, when checking to see if accessing n bytes starting at address
    "ptr" will cause a wraparound in the memory addresses, the check in
    check_bogus_address() adds an extra byte, which is incorrect, as the
    range of addresses that will be accessed is [ptr, ptr + (n - 1)].

    This can lead to incorrectly detecting a wraparound in the memory
    address, when trying to read 4 KB from memory that is mapped to the the
    last possible page in the virtual address space, when in fact, accessing
    that range of memory would not cause a wraparound to occur.

    Use the memory range that will actually be accessed when considering if
    accessing a certain amount of bytes will cause the memory address to
    wrap around.

    Link: http://lkml.kernel.org/r/1564509253-23287-1-git-send-email-isaacm@codeaurora.org
    Fixes: f5509cc18daa ("mm: Hardened usercopy")
    Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
    Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
    Co-developed-by: Prasad Sodagudi <psodagud@codeaurora.org>
    Reviewed-by: William Kucharski <william.kucharski@oracle.com>
    Acked-by: Kees Cook <keescook@chromium.org>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Trilok Soni <tsoni@codeaurora.org>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    [kees: backport to v4.14]
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    mm/usercopy.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/mm/usercopy.c
    +++ b/mm/usercopy.c
    @@ -121,7 +121,7 @@ static inline const char *check_kernel_t
    static inline const char *check_bogus_address(const void *ptr, unsigned long n)
    {
    /* Reject if object wraps past end of memory. */
    - if ((unsigned long)ptr + n < (unsigned long)ptr)
    + if ((unsigned long)ptr + (n - 1) < (unsigned long)ptr)
    return "<wrapped address>";

    /* Reject if NULL or ZERO-allocation. */

    \
     
     \ /
      Last update: 2019-08-22 19:56    [W:4.403 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site