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    Subject[PATCH 4.4 137/143] x86/a.out: Clear the dump structure initially
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Borislav Petkov <bp@suse.de>

    commit 10970e1b4be9c74fce8ab6e3c34a7d718f063f2c upstream.

    dump_thread32() in aout_core_dump() does not clear the user32 structure
    allocated on the stack as the first thing on function entry.

    As a result, the dump.u_comm, dump.u_ar0 and dump.signal which get
    assigned before the clearing, get overwritten.

    Rename that function to fill_dump() to make it clear what it does and
    call it first thing.

    This was caught while staring at a patch by Derek Robson
    <robsonde@gmail.com>.

    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: Derek Robson <robsonde@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Michael Matz <matz@suse.de>
    Cc: x86@kernel.org
    Cc: <stable@vger.kernel.org>
    Link: https://lkml.kernel.org/r/20190202005512.3144-1-robsonde@gmail.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/ia32/ia32_aout.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/arch/x86/ia32/ia32_aout.c
    +++ b/arch/x86/ia32/ia32_aout.c
    @@ -50,7 +50,7 @@ static unsigned long get_dr(int n)
    /*
    * fill in the user structure for a core dump..
    */
    -static void dump_thread32(struct pt_regs *regs, struct user32 *dump)
    +static void fill_dump(struct pt_regs *regs, struct user32 *dump)
    {
    u32 fs, gs;
    memset(dump, 0, sizeof(*dump));
    @@ -156,10 +156,12 @@ static int aout_core_dump(struct coredum
    fs = get_fs();
    set_fs(KERNEL_DS);
    has_dumped = 1;
    +
    + fill_dump(cprm->regs, &dump);
    +
    strncpy(dump.u_comm, current->comm, sizeof(current->comm));
    dump.u_ar0 = offsetof(struct user32, regs);
    dump.signal = cprm->siginfo->si_signo;
    - dump_thread32(cprm->regs, &dump);

    /*
    * If the size of the dump file exceeds the rlimit, then see

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