On Tue, Jan 09, 2024 at 12:26:13AM -0500, Sean Anderson wrote:
> Comments on NAND stuff only.
>
> On 1/8/24 12:45, Tom Rini wrote:
> > ________________________________________________________________________________________________________
> > *** CID 477216: (BAD_SHIFT)
> > /drivers/mtd/nand/raw/nand_base.c: 3921 in nand_flash_detect_onfi()
> > 3915
> > 3916 /*
> > 3917 * pages_per_block and blocks_per_lun may not be a
> > power-of-2 size
> > 3918 * (don't ask me who thought of this...). MTD assumes that
> > these
> > 3919 * dimensions will be power-of-2, so just truncate the
> > remaining area.
> > 3920 */
> > > > > CID 477216: (BAD_SHIFT)
> > > > > In expression "1 <<
> > > > > generic_fls((__u32)(__le32)p->pages_per_block) - 1", shifting by a
> > > > > negative amount has undefined behavior. The shift amount,
> > > > > "generic_fls((__u32)(__le32)p->pages_per_block) - 1", is -1.
> > 3921 mtd->erasesize = 1 <<
> > (fls(le32_to_cpu(p->pages_per_block)) - 1);
> > 3922 mtd->erasesize *= mtd->writesize;
> > 3923
> > 3924 mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);
> > 3925
> > 3926 /* See erasesize comment */
> > /drivers/mtd/nand/raw/nand_base.c: 3927 in nand_flash_detect_onfi()
> > 3921 mtd->erasesize = 1 <<
> > (fls(le32_to_cpu(p->pages_per_block)) - 1);
> > 3922 mtd->erasesize *= mtd->writesize;
> > 3923
> > 3924 mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);
> > 3925
> > 3926 /* See erasesize comment */
> > > > > CID 477216: (BAD_SHIFT)
> > > > > In expression "1 <<
> > > > > generic_fls((__u32)(__le32)p->blocks_per_lun) - 1", shifting by a
> > > > > negative amount has undefined behavior. The shift amount,
> > > > > "generic_fls((__u32)(__le32)p->blocks_per_lun) - 1", is -1.
> > 3927 chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun))
> > - 1);
> > 3928 chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
> > 3929 chip->bits_per_cell = p->bits_per_cell;
> > 3930
> > 3931 if (onfi_feature(chip) & ONFI_FEATURE_16_BIT_BUS)
> > 3932 chip->options |= NAND_BUSWIDTH_16;
>
> Yeah, this looks like a bug.
>
> > ** CID 477215: Control flow issues (MISSING_BREAK)
> > /drivers/mtd/nand/raw/nand_base.c: 4978 in nand_scan_tail()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477215: Control flow issues (MISSING_BREAK)
> > /drivers/mtd/nand/raw/nand_base.c: 4978 in nand_scan_tail()
> > 4972 pr_warn("No ECC functions supplied;
> > hardware ECC not possible\n");
> > 4973 BUG();
> > 4974 }
> > 4975 if (!ecc->read_page)
> > 4976 ecc->read_page =
> > nand_read_page_hwecc_oob_first;
> > 4977
> > > > > CID 477215: Control flow issues (MISSING_BREAK)
> > > > > The case for value "NAND_ECC_HW" is not terminated by a "break"
> > > > > statement.
> > 4978 case NAND_ECC_HW:
> > 4979 /* Use standard hwecc read page function? */
> > 4980 if (!ecc->read_page)
> > 4981 ecc->read_page = nand_read_page_hwecc;
> > 4982 if (!ecc->write_page)
> > 4983 ecc->write_page = nand_write_page_hwecc;
>
> I think we just need a fallthrough comment here.
>
> > ** CID 477214: Integer handling issues (BAD_SHIFT)
> > /drivers/mtd/nand/raw/nand_base.c: 4397 in nand_detect()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477214: Integer handling issues (BAD_SHIFT)
> > /drivers/mtd/nand/raw/nand_base.c: 4397 in nand_detect()
> > 4391
> > 4392 nand_decode_bbm_options(mtd, chip);
> > 4393
> > 4394 /* Calculate the address shift from the page size */
> > 4395 chip->page_shift = ffs(mtd->writesize) - 1;
> > 4396 /* Convert chipsize to number of pages per chip -1 */
> > > > > CID 477214: Integer handling issues (BAD_SHIFT)
> > > > > In expression "chip->chipsize >> chip->page_shift", shifting by
> > > > > a negative amount has undefined behavior. The shift amount,
> > > > > "chip->page_shift", is -1.
> > 4397 chip->pagemask = (chip->chipsize >> chip->page_shift) - 1;
> > 4398
> > 4399 chip->bbt_erase_shift = chip->phys_erase_shift =
> > 4400 ffs(mtd->erasesize) - 1;
> > 4401 if (chip->chipsize & 0xffffffff)
> > 4402 chip->chip_shift = ffs((unsigned)chip->chipsize) -
> > 1;
>
> Buggy, but only when writesize is 0 (which is a bigger bug in the nand chip).
>
> > ** CID 477213: Security best practices violations (DC.WEAK_CRYPTO)
> > /test/dm/nand.c: 67 in dm_test_nand()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477213: Security best practices violations (DC.WEAK_CRYPTO)
> > /test/dm/nand.c: 67 in dm_test_nand()
> > 61 ops.ooblen = mtd->oobsize;
> > 62 ut_assertok(mtd_read_oob(mtd, mtd->erasesize, &ops));
> > 63 ut_asserteq(0, oob[mtd_to_nand(mtd)->badblockpos]);
> > 64
> > 65 /* Generate some data and write it */
> > 66 for (i = 0; i < size / sizeof(int); i++)
> > > > > CID 477213: Security best practices violations (DC.WEAK_CRYPTO)
> > > > > "rand" should not be used for security-related applications,
> > > > > because linear congruential algorithms are too easy to break.
> > 67 gold[i] = rand();
> > 68 ut_assertok(nand_write_skip_bad(mtd, off, &length, NULL, U64_MAX,
> > 69 (void *)gold, 0));
> > 70 ut_asserteq(size, length);
> > 71
> > 72 /* Verify */
>
> Not a bug.
>
> > ** CID 477211: API usage errors (ALLOC_FREE_MISMATCH)
> > /drivers/mtd/nand/raw/nand_bbt.c: 1133 in nand_scan_bbt()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477211: API usage errors (ALLOC_FREE_MISMATCH)
> > /drivers/mtd/nand/raw/nand_bbt.c: 1133 in nand_scan_bbt()
> > 1127
> > 1128 /* Prevent the bbt regions from erasing / writing */
> > 1129 mark_bbt_region(mtd, td);
> > 1130 if (md)
> > 1131 mark_bbt_region(mtd, md);
> > 1132
> > > > > CID 477211: API usage errors (ALLOC_FREE_MISMATCH)
> > > > > Calling "vfree" frees "buf" using "vfree" but it should have
> > > > > been freed using "kfree". [Note: The source code implementation of
> > > > > the function has been overridden by a builtin model.]
> > 1133 vfree(buf);
> > 1134 return 0;
> > 1135
> > 1136 err:
> > 1137 kfree(this->bbt);
> > 1138 this->bbt = NULL;
>
> Not a bug, since these both call free().
>
> > ** CID 477210: Security best practices violations (DC.WEAK_CRYPTO)
> > /drivers/mtd/nand/raw/sand_nand.c: 199 in sand_nand_read()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477210: Security best practices violations (DC.WEAK_CRYPTO)
> > /drivers/mtd/nand/raw/sand_nand.c: 199 in sand_nand_read()
> > 193 chip->tmp_dirty = true;
> > 194 for (i = 0; i < chip->err_steps; i++) {
> > 195 u32 bit_errors = chip->err_count;
> > 196 unsigned int j = chip->err_step_bits +
> > chip->ecc_bits;
> > 197
> > 198 while (bit_errors) {
> > > > > CID 477210: Security best practices violations (DC.WEAK_CRYPTO)
> > > > > "rand" should not be used for security-related applications,
> > > > > because linear congruential algorithms are too easy to break.
> > 199 unsigned int u = rand();
> > 200 float quot = 1ULL << 32;
> > 201
> > 202 do {
> > 203 quot *= j - bit_errors;
> > 204 quot /= j;
>
> Not a bug.
>
> > ** CID 477207: Control flow issues (MISSING_BREAK)
> > /drivers/mtd/nand/raw/nand_base.c: 4969 in nand_scan_tail()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477207: Control flow issues (MISSING_BREAK)
> > /drivers/mtd/nand/raw/nand_base.c: 4969 in nand_scan_tail()
> > 4963 /*
> > 4964 * Check ECC mode, default to software if
> > 3byte/512byte hardware ECC is
> > 4965 * selected and we have 256 byte pagesize fallback to
> > software ECC
> > 4966 */
> > 4967
> > 4968 switch (ecc->mode) {
> > > > > CID 477207: Control flow issues (MISSING_BREAK)
> > > > > The case for value "NAND_ECC_HW_OOB_FIRST" is not terminated by
> > > > > a "break" statement.
> > 4969 case NAND_ECC_HW_OOB_FIRST:
> > 4970 /* Similar to NAND_ECC_HW, but a separate
> > read_page handle */
> > 4971 if (!ecc->calculate || !ecc->correct ||
> > !ecc->hwctl) {
> > 4972 pr_warn("No ECC functions supplied;
> > hardware ECC not possible\n");
> > 4973 BUG();
> > 4974 }
>
> need a fallthrough comment
>
> > ** CID 477205: Integer handling issues (OVERFLOW_BEFORE_WIDEN)
> > /cmd/mtd.c: 88 in mtd_dump_device_buf()
> >
> >
> > ________________________________________________________________________________________________________
> > *** CID 477205: Integer handling issues (OVERFLOW_BEFORE_WIDEN)
> > /cmd/mtd.c: 88 in mtd_dump_device_buf()
> > 82 printf("\nDump %d data bytes from 0x%08llx:\n",
> > 83 mtd->writesize, start_off + data_off);
> > 84 mtd_dump_buf(&buf[data_off],
> > 85 mtd->writesize, start_off + data_off);
> > 86
> > 87 if (woob) {
> > > > > CID 477205: Integer handling issues (OVERFLOW_BEFORE_WIDEN)
> > > > > Potentially overflowing expression "page * mtd->oobsize" with
> > > > > type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit
> > > > > arithmetic, and then used in a context that expects an expression of
> > > > > type "u64" (64 bits, unsigned).
> > 88 u64 oob_off = page * mtd->oobsize;
> > 89
> > 90 printf("Dump %d OOB bytes from page at
> > 0x%08llx:\n",
> > 91 mtd->oobsize, start_off + data_off);
> > 92 mtd_dump_buf(&buf[len + oob_off],
> > 93 mtd->oobsize, 0);
>
> In the Linux MTD list [1], the largest this can be is 0xe0000000 for
> MT29F512G08CUCAB. That's worryingly
> close to overflow, so I'd say this is a bug.Thanks, I've updated the not a bug ones in the dashboard. -- Tom
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