[Xen-changelog] [xen staging] console: avoid buffer overflow in guest_console_write()

[patchbot@xxxxxxx]

commit aaf8839fdf8b9b1a93a3837b82f680adea1b297c
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Nov 29 17:08:20 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Nov 29 17:08:20 2019 +0100

    console: avoid buffer overflow in guest_console_write()
    
    The switch of guest_console_write()'s second parameter from plain to
    unsigned int has caused the function's main loop header to no longer
    guard the min_t() use within the function against effectively negative
    values, due to the casts hidden inside the macro. Replace by a plain
    min(), casting one of the arguments as necessary.
    
    Fixes: ea601ec9995b ("xen/console: Rework HYPERCALL_console_io interface")
    Reported-by: Ilja Van Sprundel <ivansprundel@xxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Julien Grall <julien@xxxxxxx>
---
 xen/drivers/char/console.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index e133534be7..aa72bd1244 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -538,7 +538,7 @@ static long 
guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer,
                 __HYPERVISOR_console_io, "iih",
                 CONSOLEIO_write, count, buffer);
 
-        kcount = min_t(int, count, sizeof(kbuf)-1);
+        kcount = min((size_t)count, sizeof(kbuf) - 1);
         if ( copy_from_guest(kbuf, buffer, kcount) )
             return -EFAULT;
 
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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