Hi Lothar,

On Tue, Feb 08, 2011 at 12:41:20PM +0100, Lothar Wa?mann wrote:

Hi,

Shawn Guo writes:
[...]

quoted

+static int mxs_mmc_remove(struct platform_device *pdev)
+{
+	struct mmc_host *mmc = platform_get_drvdata(pdev);
+	struct mxs_mmc_host *host = mmc_priv(mmc);
+
+	platform_set_drvdata(pdev, NULL);
+
+	mmc_remove_host(mmc);
+
+	del_timer(&host->timer);
+
+	free_irq(host->irq, host);
+
+	if (host->dmach)
+		dma_release_channel(host->dmach);
+
+	clk_disable(host->clk);
+	clk_put(host->clk);
+
+	iounmap(host->base);
+
+	mmc_free_host(mmc);
+
+	release_mem_region(host->res->start, resource_size(host->res));

When compiled with CONFIG_PAGE_POISON this leads to:
|mmc0: card cdef removed
|Unable to handle kernel paging request at virtual address 6b6b6b6b
|pgd = c6ea4000
|[6b6b6b6b] *pgd=00000000
|Internal error: Oops: 1 [#1] PREEMPT
|last sysfs file: /sys/module/mxs_mmc/refcnt
|Modules linked in: mxs_mmc(-) evdev nand nand_ids nand_ecc tsc2007 pca953x
|CPU: 0    Not tainted  (2.6.37-karo+ #100)
|PC is at mxs_mmc_remove+0x78/0x94 [mxs_mmc]
|LR is at mark_held_locks+0x5c/0x84
|pc : [<bf03310c>]    lr : [<c0071da0>]    psr: 20000013
|sp : c6e33ef8  ip : 6b6b6b6b  fp : be825a38
|r10: 00000000  r9 : c6e32000  r8 : c0037888
|r7 : 00591700  r6 : c78d24bc  r5 : c6c6ea80  r4 : c6c6ed60
|r3 : 6b6b6b6b  r2 : 00000040  r1 : c6d833d0  r0 : c043af18
|Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
|Control: 0005317f  Table: 46ea4000  DAC: 00000015
|Process modprobe (pid: 1217, stack limit = 0xc6e32270)
|Stack: (0xc6e33ef8 to 0xc6e34000)
|3ee0:                                                       c78d2488 bf034100
|3f00: c78d24bc c0237034 c78d2488 c0235e68 c78d2488 bf034100 c78d24bc c0235f34
|3f20: bf034100 00000080 c045c3e8 c02351c4 bf034138 00000080 c6e33f44 c007de4c
|3f40: be82599c 5f73786d 00636d6d 00000000 c01efdf0 c6d830c0 c6d830c0 c03195ec
|3f60: 00000001 c6dddbd8 c6e33f7c c0045fc4 c6d830c0 c00377d8 00000001 00000081
|3f80: 60000010 c00720d4 be825a2c 00000000 00000001 be825a2c 005916b0 00000001
|3fa0: 00000081 c00376c0 be825a2c 005916b0 00591700 00000080 be825994 00000000
|3fc0: be825a2c 005916b0 00000001 00000081 00591700 0000c69c 005916bc be825a38
|3fe0: 00591520 be8259a0 0000a42c 402aee3c 60000010 00591700 aaaaaaaa aaaaaaaa
|[<bf03310c>] (mxs_mmc_remove+0x78/0x94 [mxs_mmc]) from [<c0237034>] (platform_drv_remove+0x18/0x1c)
|[<c0237034>] (platform_drv_remove+0x18/0x1c) from [<c0235e68>] (__device_release_driver+0x64/0xa4)
|[<c0235e68>] (__device_release_driver+0x64/0xa4) from [<c0235f34>] (driver_detach+0x8c/0xb4)
|[<c0235f34>] (driver_detach+0x8c/0xb4) from [<c02351c4>] (bus_remove_driver+0x8c/0xb4)
|[<c02351c4>] (bus_remove_driver+0x8c/0xb4) from [<c007de4c>] (sys_delete_module+0x1f4/0x260)
|[<c007de4c>] (sys_delete_module+0x1f4/0x260) from [<c00376c0>] (ret_fast_syscall+0x0/0x38)
|Code: e1a00005 eb48cd47 e5943008 e59f0014 (e8930006) 
|---[ end trace bb06175839554c3b ]---
indicating a use_after_free BUG!

Thanks for catching this.

The struct mxs_mmc_host has been already freed here by the
preceding mmc_free_host() call. This should be:
	struct resource *res = host->res;
...
	mmc_free_host(mmc);
	release_mem_region(res->start, resource_size(res));

How about fixing it like below?

	release_mem_region(host->res->start, resource_size(host->res));
	mmc_free_host(mmc);

Regards,
Shawn