• Frederic Weisbecker's avatar
    perf_counter: Zero dead bytes from ftrace raw samples size alignment · 1853db0e
    Frederic Weisbecker authored
    
    
    After aligning the ftrace raw samples, there are dead bytes storing
    random data from the stack. We don't want to leak these to userspace,
    then zero these out.
    
    Before:
    
    	0x2de88 [0x50]: event: 9
    	.
    	. ... raw event: size 80 bytes
    	.  0000:  09 00 00 00 01 00 50 00 d0 c7 00 81 ff ff ff ff  ......P........
    	.  0010:  68 01 00 00 68 01 00 00 2c 00 00 00 00 00 00 00  h...h...,......
    	.  0020:  2c 00 00 00 2b 00 01 02 68 01 00 00 68 01 00 00  ,...+...h...h..
    	.  0030:  6b 6f 6e 64 65 6d 61 6e 64 2f 30 00 00 00 00 00  kondemand/0....
    	.  0040:  68 01 00 00 40 7f 46 81 ff ff ff ff 00 10 1b 7f  h...@.F........
                                                          ^  ^  ^  ^
                                                             Leak
    
    After:
    
    	0x2d318 [0x50]: event: 9
    	.
    	. ... raw event: size 80 bytes
    	.  0000:  09 00 00 00 01 00 50 00 d0 c7 00 81 ff ff ff ff  ......P........
    	.  0010:  68 01 00 00 68 01 00 00 68 14 00 00 00 00 00 00  h...h...h......
    	.  0020:  2c 00 00 00 2b 00 01 02 68 01 00 00 68 01 00 00  ,...+...h...h..
    	.  0030:  6b 6f 6e 64 65 6d 61 6e 64 2f 30 00 00 00 00 00  kondemand/0....
    	.  0040:  68 01 00 00 a0 80 46 81 ff ff ff ff 00 00 00 00  h.....F........
                                                          ^  ^  ^  ^
    							 Fixed
    Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Mike Galbraith <efault@gmx.de>
    LKML-Reference: <1249915116-5210-1-git-send-email-fweisbec@gmail.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Mike Galbraith <efault@gmx.de>
    1853db0e