Re: [patch] fbcon: don't use vc_resize() on initialization
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2009-07-30 23:12:27
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On Wed, 29 Jul 2009 19:21:23 +0200 Johannes Weiner [off-list ref] 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?
quoted hunk
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 <redacted> --- 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);