Test/upstream track - #69
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Signed-off-by: prouthu <prouthu@qti.qualcomm.com>
Signed-off-by: prouthu <prouthu@qti.qualcomm.com>
Signed-off-by: prouthu-qti <prouthu@qti.qualcomm.com>
Signed-off-by: prouthu <prouthu@qti.qualcomm.com>
Signed-off-by: prouthu-qti <prouthu@qti.qualcomm.com>
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[BUG] Recently, we encountered a KASAN warning as follows: BUG: KASAN: slab-out-of-bounds in ccw_putcs+0x8bd/0xa80 Read of size 1 at addr ff11000110067100 by task bash/1209 CPU: 10 UID: 0 PID: 1209 Comm: bash Not tainted 7.2.0-rc3 #69 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 Call Trace: <TASK> ... kasan_report+0xf0/0x120 ? ccw_putcs+0x8bd/0xa80 ccw_putcs+0x8bd/0xa80 ? __pfx_ccw_putcs+0x10/0x10 fbcon_putcs+0x338/0x410 ? __pfx_ccw_putcs+0x10/0x10 do_update_region+0x21d/0x450 invert_screen+0x29d/0x5e0 ? __kmalloc_noprof+0x493/0x640 ? vc_do_resize+0x17c/0xe50 clear_selection+0x4c/0x60 vc_do_resize+0xaee/0xe50 fbcon_modechanged+0x2bd/0x640 rotate_all_store+0x298/0x380 ... reproduce: 1) issue two ioctls: first a KDFONTOP ioctl with op.op = KD_FONT_OP_SET, op.width = 1 and op.height = 1, then a TIOCL_SETSEL ioctl 2) echo 2 > /sys/devices/virtual/graphics/fbcon/rotate_all 3) issue two ioctls: first a KDFONTOP ioctl with op.op = KD_FONT_OP_SET, op.width = 8 and op.height = 1, then a TIOCL_SETSEL ioctl 4) echo 3 > /sys/devices/virtual/graphics/fbcon/rotate_all [CAUSE] The root cause is that fbcon_modechanged() first sets the current rotate's corresponding ops. Subsequently, during vc_resize(), it may trigger clear_selection(), and in fbcon_putcs->ccw_putcs[rotate=3], this can result in an out-of-bounds access to "src". This happens because par->rotated.buf is reallocated in fbcon_rotate_font(): 1) When rotate=2, its size is (width + 7) / 8 * height 2) When rotate=3, its size is (height + 7) / 8 * width And the call to fbcon_rotate_font() occurs after clear_selection(). In other words, the fontbuffer is allocated using the size calculated from the previous rotation 2, but before reallocating it with the new size, con_putcs is already using the new rotation 3: rotate_all_store fbcon_rotate_all fbcon_set_all_vcs fbcon_modechanged set_blitting_type ... par->bitops = &ccw_fbcon_bitops vc_resize ... clear_selection highlight ... do_update_region fbcon_putcs ... image.dy = vyres - ((xx + count) * vc->vc_font.width) [1] // overflow! ccw_putcs_aligned // old buf size is still being used during the read! src = par->rotated.buf + (scr_readw(s--) & charmask) * cellsize fb_pad_aligned_buffer----[src KASAN!!!] [2] info->fbops->fb_imageblit(info, image) sys_imageblit fb_imageblit fb_address_forward // offset: image->dy * bits_per_line + image->dx * bpp unsigned int bits = (unsigned int)adr->bits + offset adr->address += (bits & ~(BITS_PER_LONG - 1u)) / BITS_PER_BYTE [3] fb_bitmap_imageblit ... fb_read_offset // page fault! [4] update_screen redraw_screen ... ccw_cursor soft_cursor memcpy(src, image->data, dsize)----[src KASAN again!!!] [5] fbcon_switch fbcon_rotate_font font_data_rotate dst = kmalloc_array(charcount, d_cellsize, GFP_KERNEL) // the new size is allocated only here! par->rotated.buf = buf [6] [FIX] A fairly obvious approach is to follow fbcon_switch(): in fbcon_modechanged(), call rotate_font() before vc_resize() so that a correctly sized buffer is allocated in time, as done in [6]. This fix is necessary, but it is not sufficient on its own. In [1] it causes an image.dy overflow (ccw_putcs: vyres = 768, image.dy = 4294967040), because vc_cols has not been updated in time at this point (it is likewise only updated after clear_selection()). This allows (xx + count) * width to exceed vyres, causing image.dy to overflow. Subsequently, address in [3] is incremented by an even larger amount, which triggers a page fault at [4]. Therefore, a second fix is required in combination with the first: move clear_selection() earlier, before set_blitting_type() in fbcon_set_all_vcs(), to prevent the out-of-bounds access. fbcon_rotate() has a similar problem, so add the same clear there. Since vc_is_sel() is not exported, the fbdev side is currently forced to call clear_selection() unconditionally, causing the global selection to be cleared prematurely. And this will not cause any other significant impact. Signed-off-by: Zizhi Wo <wozizhi@huawei.com> Signed-off-by: Helge Deller <deller@gmx.de>
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