i2c-mlxbf.c: prevent stack overflow in mlxbf_i2c_smbus_start_transaction

[Asmaa Mnebhi]

SRU Justification:

[Impact]

There could be stack overflow in mlxbf_i2c_smbus_start_transaction().
memcpy() is called in a loop while 'operation->length' upper bound is not
checked and 'data_idx' also increments.

More details:
The operation length is verified by the caller functions so it cannot exceed I2C_SMBUS_BLOCK_MAX bytes (32 bytes) for each operation that is a part of the write. Data_desc array is 128 bytes in size. So potentially a request which consists of 4 writes, 32 bytes each can trigger an off-by-one or off-by-two overflow, because the first byte of data_desc is used by addr, effectively decreasing the available data_desc buffer size by one. Functions like mlx_smbus_i2c_block_func() that prepare the request also set the length of the first write operation to one and store the command id there, so the target buffer size again decreases data_desc by one, making it two bytes less than expected.

[Fix]

* Add a check for "operation->length" and data_idx and return error if reached upper bound.

[Test Case]

* Test the i2c-mlxbf.c driver using IPMB functionality.

[Regression Potential]

This fix returns a negative value to indicate that a transaction has failed. So it will catch more transactions failures.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-bluefield - 5.4.0-1019.22

---------------
linux-bluefield (5.4.0-1019.22) focal; urgency=medium

  * focal/linux-bluefield: 5.4.0-1019.22 -proposed tracker (LP: #1942533)

  * Focal update: v5.4.134 upstream stable release (LP: #1939440)
    - [Config] bluefield: CONFIG_BATTERY_RT5033=m

  * Fix fragmentation support for TC connection tracking (LP: #1940872)
    - net/sched: act_ct: fix restore the qdisc_skb_cb after defrag
    - net/sched: act_ct: fix miss set mru for ovs after defrag in act_ct
    - net/sched: fix miss init the mru in qdisc_skb_cb
    - net/sched: act_ct: fix wild memory access when clearing fragments
    - Revert "net/sched: act_ct: Fix skb double-free in tcf_ct_handle_fragments()
      error flow"
    - net/sched: act_mirred: refactor the handle of xmit
    - net/sched: The error lable position is corrected in ct_init_module
    - net/sched: sch_frag: add generic packet fragment support.
    - ipv6: add ipv6_fragment hook in ipv6_stub

  * Add the upcoming BlueField-3 device ID (LP: #1941803)
    - net/mlx5: Update the list of the PCI supported devices

  * CT state not reset when packet redirected to different port (LP: #1940448)
    - Revert "UBUNTU: SAUCE: net/sched: act_mirred: Reset ct when reinserting skb
      back into queue"
    - net: sched: act_mirred: Reset ct info when mirror/redirect skb

  * Export xfrm_policy_lookup_bytype function (LP: #1934313)
    - SAUCE: xfrm: IPsec Export xfrm_policy_lookup_bytype function

  [ Ubuntu: 5.4.0-85.95 ]

  * focal/linux: 5.4.0-85.95 -proposed tracker (LP: #1942557)
  * please drop virtualbox-guest-dkms virtualbox-guest-source (LP: #1933248)
    - [Config] Disable virtualbox dkms build
  * Packaging resync (LP: #1786013)
    - debian/dkms-versions -- update from kernel-versions (main/2021.09.06)
  * LRMv5: switch primary version handling to kernel-versions data set
    (LP: #1928921)
    - [Packaging] switch to kernel-versions
  * disable “CONFIG_HISI_DMA” config for ubuntu version (LP: #1936771)
    - Disable CONFIG_HISI_DMA
    - [Config] Record hisi_dma no longer built for arm64
  * memory leaking when removing a profile (LP: #1939915)
    - apparmor: Fix memory leak of profile proxy
  * CryptoExpress EP11 cards are going offline (LP: #1939618)
    - s390/zcrypt: Support for CCA protected key block version 2
    - s390: Replace zero-length array with flexible-array member
    - s390/zcrypt: Use scnprintf() for avoiding potential buffer overflow
    - s390/zcrypt: replace snprintf/sprintf with scnprintf
    - s390/ap: Remove ap device suspend and resume callbacks
    - s390/zcrypt: use fallthrough;
    - s390/zcrypt: use kvmalloc instead of kmalloc for 256k alloc
    - s390/ap: remove power management code from ap bus and drivers
    - s390/ap: introduce new ap function ap_get_qdev()
    - s390/zcrypt: use kzalloc
    - s390/zcrypt: fix smatch warnings
    - s390/zcrypt: code beautification and struct field renames
    - s390/zcrypt: split ioctl function into smaller code units
    - s390/ap: rename and clarify ap state machine related stuff
    - s390/zcrypt: provide cex4 cca sysfs attributes for cex3
    - s390/ap: rework cry...