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Date:   Thu, 14 Apr 2022 20:09:07 +0530
From:   Manivannan Sadhasivam <mani@kernel.org>
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     Md Sadre Alam <quic_mdalam@quicinc.com>, mani@kernel.org,
        richard@nod.at, vigneshr@ti.com, linux-mtd@lists.infradead.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        konrad.dybcio@somainline.org, quic_srichara@quicinc.com
Subject: Re: [PATCH] mtd: rawnand: qcom: fix memory corruption that causes
 panic
Message-ID: <20220414143907.GA20493@thinkpad>
References: <1649914773-22434-1-git-send-email-quic_mdalam@quicinc.com>
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 <2697e757-f446-9cdb-95e0-ea01a642e6d4@quicinc.com>
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On Thu, Apr 14, 2022 at 02:42:36PM +0200, Miquel Raynal wrote:
> Hi Md,
> 
> quic_mdalam@quicinc.com wrote on Thu, 14 Apr 2022 17:50:48 +0530:
> 
> > > Hi Md,
> > >
> > > quic_mdalam@quicinc.com wrote on Thu, 14 Apr 2022 11:09:33 +0530:
> > >  
> > >> This patch fixes a memory corruption that occurred in the
> > >> nand_scan() path for Hynix nand device.
> > >>
> > >> On boot, for Hynix nand device will panic at a weird place:
> > >> | Unable to handle kernel NULL pointer dereference at virtual
> > >>    address 00000070
> > >> | [00000070] *pgd=00000000
> > >> | Internal error: Oops: 5 [#1] PREEMPT SMP ARM Modules linked in:
> > >> | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-01473-g13ae1769cfb0
> > >>    #38
> > >> | Hardware name: Generic DT based system PC is at
> > >> | nandc_set_reg+0x8/0x1c LR is at qcom_nandc_command+0x20c/0x5d0
> > >> | pc : [<c088b74c>]    lr : [<c088d9c8>]    psr: 00000113
> > >> | sp : c14adc50  ip : c14ee208  fp : c0cc970c
> > >> | r10: 000000a3  r9 : 00000000  r8 : 00000040
> > >> | r7 : c16f6a00  r6 : 00000090  r5 : 00000004  r4 :c14ee040
> > >> | r3 : 00000000  r2 : 0000000b  r1 : 00000000  r0 :c14ee040
> > >> | Flags: nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM Segment none
> > >> | Control: 10c5387d  Table: 8020406a  DAC: 00000051 Register r0
> > >> | information: slab kmalloc-2k start c14ee000 pointer offset
> > >>    64 size 2048
> > >> | Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) nandc_set_reg
> > >> | from qcom_nandc_command+0x20c/0x5d0 qcom_nandc_command from
> > >> | nand_readid_op+0x198/0x1e8 nand_readid_op from
> > >> | hynix_nand_has_valid_jedecid+0x30/0x78
> > >> | hynix_nand_has_valid_jedecid from hynix_nand_init+0xb8/0x454
> > >> | hynix_nand_init from nand_scan_with_ids+0xa30/0x14a8
> > >> | nand_scan_with_ids from qcom_nandc_probe+0x648/0x7b0
> > >> | qcom_nandc_probe from platform_probe+0x58/0xac
> > >>
> > >> The problem is that the nand_scan()'s qcom_nand_attach_chip callback
> > >> is updating the nandc->max_cwperpage from 1 to 4.This causes the
> > >> sg_init_table of clear_bam_transaction() in the driver's
> > >> qcom_nandc_command() to memset much more than what was initially
> > >> allocated by alloc_bam_transaction().  
> > > Thanks for investigating!
> > >  
> > >> This patch will update nandc->max_cwperpage 1 to 4 after nand_scan()
> > >> returns, and remove updating nandc->max_cwperpage from
> > >> qcom_nand_attach_chip call back.  
> > > The fix does not look right, as far as I understand, this should be properly handled during the attach phase. That is where we have all information about the chip and do the configuration for this chip.
> > >
> > > If you update max_cwperpage there you should probably update other internal variables that depend on it as well.  
> > 
> >  ?? Currently we are updating max_cwperpage? in qcom_nand_attach_chip(), but we are seeing issue for Hynix nand device since nand_scan_tail() is getting called after nand_attach() and in nand_attach() we are updating max_cwperpage to 4 or 8 based on page size.
> > 
> >  ??? From nand_scan_tail() there is a call for nand_manufacturer_init() , specific to Hynix nand read_id is getting called that's why we are seeing this issue only for Hynix nand device. Read id sequence as below
> > 
> >  ?? hynix_nand_has_valid_jedecid()
> > 
> >  ??????? ? ? ? ? |
> > 
> >  ?? nand_readid_op()
> > 
> >  ???????????? |
> > 
> >  ?qcom_nandc_command()
> > 
> >  ??????????? |
> > 
> > pre_command()
> > 
> >  ????????? |
> > 
> > clear_bam_transaction()?? --> In this call we are doing sg_init_table() which is calling memset() based on max_cwperpage.Since initially we have allocated bam transaction as per max_cwperpage =1 and , since nand_chip_attach() updated max_cwperpage,? now we are doing memset as per max_cwperpage = 4 or 8.
> > 
> > 
> > So anyway we have to updated max_cwperpage after nand_scan() call only.? Since there is no other dependency on max_cwperpage in nand_attach_chip() and we are using this in bam_alloc() and bam_clear().
> 
> Why don't you update the sg table after increasing max_cwperpage?
> 

Or we could move the bam reallocation inside qcom_nand_attach_chip() as below?

diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
index 7c6efa3b6255..58c16054630f 100644
--- a/drivers/mtd/nand/raw/qcom_nandc.c
+++ b/drivers/mtd/nand/raw/qcom_nandc.c
@@ -2653,9 +2653,23 @@ static int qcom_nand_attach_chip(struct nand_chip *chip)
 
        mtd_set_ooblayout(mtd, &qcom_nand_ooblayout_ops);
 
+       /* Free the initially allocated BAM transaction for reading the ONFI params */
+       if (nandc->props->is_bam)
+               free_bam_transaction(nandc);
+
        nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
                                     cwperpage);
 
+       /* Now allocate the BAM transaction based on updated max_cwperpage */
+       if (nandc->props->is_bam) {
+               nandc->bam_txn = alloc_bam_transaction(nandc);
+               if (!nandc->bam_txn) {
+                       dev_err(nandc->dev,
+                               "failed to allocate bam transaction\n");
+                       return -ENOMEM;
+               }
+       }
+
        /*
         * DATA_UD_BYTES varies based on whether the read/write command protects
         * spare data with ECC too. We protect spare data by default, so we set
@@ -2956,17 +2970,6 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
        if (ret)
                return ret;
 
-       if (nandc->props->is_bam) {
-               free_bam_transaction(nandc);
-               nandc->bam_txn = alloc_bam_transaction(nandc);
-               if (!nandc->bam_txn) {
-                       dev_err(nandc->dev,
-                               "failed to allocate bam transaction\n");
-                       nand_cleanup(chip);
-                       return -ENOMEM;
-               }
-       }
-
        ret = mtd_device_parse_register(mtd, probes, NULL, NULL, 0);
        if (ret)
                nand_cleanup(chip);

Thanks,
Mani