lkml.org 
[lkml]   [2014]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.15 035/139] arm64: ptrace: change fs when passing kernel pointer to regset code
    Date
    3.15-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Will Deacon <will.deacon@arm.com>

    commit c168870704bcde6bb63d05f7882b620dd3985a46 upstream.

    Our compat PTRACE_POKEUSR implementation simply passes the user data to
    regset_copy_from_user after some simple range checking. Unfortunately,
    the data in question has already been copied to the kernel stack by this
    point, so the subsequent access_ok check fails and the ptrace request
    returns -EFAULT. This causes problems tracing fork() with older versions
    of strace.

    This patch briefly changes the fs to KERNEL_DS, so that the access_ok
    check passes even with a kernel address.

    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm64/kernel/ptrace.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/arch/arm64/kernel/ptrace.c
    +++ b/arch/arm64/kernel/ptrace.c
    @@ -821,6 +821,7 @@ static int compat_ptrace_write_user(stru
    compat_ulong_t val)
    {
    int ret;
    + mm_segment_t old_fs = get_fs();

    if (off & 3 || off >= COMPAT_USER_SZ)
    return -EIO;
    @@ -828,10 +829,13 @@ static int compat_ptrace_write_user(stru
    if (off >= sizeof(compat_elf_gregset_t))
    return 0;

    + set_fs(KERNEL_DS);
    ret = copy_regset_from_user(tsk, &user_aarch32_view,
    REGSET_COMPAT_GPR, off,
    sizeof(compat_ulong_t),
    &val);
    + set_fs(old_fs);
    +
    return ret;
    }




    \
     
     \ /
      Last update: 2014-06-28 21:21    [W:4.124 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site