Messages in this thread | | | Date | Thu, 30 Jul 2009 16:11:49 -0700 | From | Andrew Morton <> | Subject | Re: [patch] fbcon: don't use vc_resize() on initialization |
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On Wed, 29 Jul 2009 19:21:23 +0200 Johannes Weiner <hannes@cmpxchg.org> wrote:
> Catalin and kmemleak spotted a leak of a VC screen buffer in > vc_allocate() due to the following chain of events: > > vc_allocate() > visual_init(init=1) > vc->vc_sw->con_init(init=1) > fbcon_init() > vc_resize() > vc->screen_buf = kmalloc() > vc->screen_buf = kmalloc() > > The common way for the VC drivers is to set the screen dimension > parameters manually in the init case and only call vc_resize() for > !init - which allocates a screen buffer according to the new > dimensions. > > fbcon instead would do vc_resize() unconditionally and afterwards set > the dimensions manually (again) for !init - i.e. completely upside > down. The vc_resize() allocated buffer would then get lost by > vc_allocate() allocating a fresh one. > > Use vc_resize() only for actual resizing to close the leak. > > Set the dimensions manually only in initialization mode to remove the > redundant setting in resize mode. > > The kmemleak trace from Catalin: > > unreferenced object 0xde158000 (size 12288):
That's a big leak!
What sequence of user actions would cause it to occur?
> comm "Xorg", pid 1439, jiffies 4294961016 > hex dump (first 32 bytes): > 20 00 20 00 20 00 20 00 20 00 20 00 20 00 20 00 . . . . . . . . > 20 00 20 00 20 00 20 00 20 00 20 00 20 00 20 00 . . . . . . . . > backtrace: > [<c006f74b>] __save_stack_trace+0x17/0x1c > [<c006f81d>] create_object+0xcd/0x188 > [<c01f5457>] kmemleak_alloc+0x1b/0x3c > [<c006e303>] __kmalloc+0xdb/0xe8 > [<c012cc4b>] vc_do_resize+0x73/0x1e0 > [<c012cdf1>] vc_resize+0x15/0x18 > [<c011afc1>] fbcon_init+0x1f9/0x2b8 > [<c0129e87>] visual_init+0x9f/0xdc > [<c012aff3>] vc_allocate+0x7f/0xfc > [<c012b087>] con_open+0x17/0x80 > [<c0120e43>] tty_open+0x1f7/0x2e4 > [<c0072fa1>] chrdev_open+0x101/0x118 > [<c006ffad>] __dentry_open+0x105/0x1cc > [<c00700fd>] nameidata_to_filp+0x2d/0x38 > [<c00788cd>] do_filp_open+0x2c1/0x54c > [<c006fdff>] do_sys_open+0x3b/0xb4 > > Reported-by: Catalin Marinas <catalin.marinas@arm.com> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > Tested-by: Catalin Marinas <catalin.marinas@arm.com> > Cc: Pekka Enberg <penberg@cs.helsinki.fi> > --- > drivers/video/console/fbcon.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c > index 471a9a6..3a44695 100644 > --- a/drivers/video/console/fbcon.c > +++ b/drivers/video/console/fbcon.c > @@ -1082,7 +1082,6 @@ static void fbcon_init(struct vc_data *vc, int init) > new_rows = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres); > new_cols /= vc->vc_font.width; > new_rows /= vc->vc_font.height; > - vc_resize(vc, new_cols, new_rows); > > /* > * We must always set the mode. The mode of the previous console > @@ -1111,10 +1110,11 @@ static void fbcon_init(struct vc_data *vc, int init) > * vc_{cols,rows}, but we must not set those if we are only > * resizing the console. > */ > - if (!init) { > + if (init) { > vc->vc_cols = new_cols; > vc->vc_rows = new_rows; > - } > + } else > + vc_resize(vc, new_cols, new_rows); > > if (logo) > fbcon_prepare_logo(vc, info, cols, rows, new_cols, new_rows);
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