Patch Name:  PHKL_6783

Patch Description: s700 10.01 Fix for bmap() panic and data corruption

Creation Date: 96/02/07

Post Date:  96/04/01

Hardware Platforms - OS Releases:
        s700: 10.01

Products: N/A

Filesets:
        OS-Core.CORE-KRN

Automatic Reboot?: Yes

Status: General Release

Critical:
        Yes
        PHKL_6783: PANIC CORRUPTION

Path Name:  /hp-ux_patches/s700/10.X/PHKL_6783

Symptoms:
        PHKL_6783:
        The possible symptoms are:
        1. panics with data segmentation fault:
           trap type 15, pcsq.pcoq = 0.790d0, isr.ior = 0.8034b544
             panic: Data segmentation fault
             panic+0x001c   trap+0x0aac    $thndlr_rtn+0x0000
             bmap+0x08b8    rwip+0x0518    ufs_rdwr+0x02c4
             vno_rw+0x009c  rwuio+0x0154   write+0x006c
        2. Buffer cache corruption resulting in file-system panics
           or in user data corruption. The corruption would appear
           as being cache line aligned.

Defect Description:
        PHKL_6783:
        Due to a defect in bmap(), there was a window for a race
        condition where bmap() could reference a buffer after it
        had been handed back to the buffer cache.  If the buffer
        was already reallocated to hold less pages, bmap() could
        then access an invalid page causing a panic data
        segmentation fault.
        Another insidious symptom could be data corruption in the
        buffer cache if the released buffer was re-used and an
        I/O was in progress (DMA transfer): accessing the buffer
        data would validate data cache lines for which we would
        have done a data cache flush prior to starting the I/O.
        Looking at the buffer data after the I/O completion would
        then show stale data and not the data just DMA'ed into
        the buffer.
        A buffer cache rule is "access buffer data only when
        owning the buffer" and bmap() was breaking this rule.
        The race condition is more likely to occur when doing
        synchronous writes as with O_SYNC.

SR:
        5000713354

Patch Files:
        /usr/conf/lib/libufs.a(ufs_bmap.o)

what(1) Output:
        /usr/conf/lib/libufs.a(ufs_bmap.o):
                ufs_bmap.c $Date: 96/02/06 11:55:33 $ $Revision: 1.2
                        2.72.20 $ PATCH_10.01 (PHKL_6783)

cksum(1) Output:
        4196168200 4984 /usr/conf/lib/libufs.a(ufs_bmap.o)

Patch Conflicts: None

Patch Dependencies:  None

Hardware Dependencies:  None

Other Dependencies:  None

Supersedes:  None

Equivalent Patches:
        PHKL_6784:
        s800: 10.01

        PHKL_6092:
        s800: 9.00

        PHKL_6093:
        s800: 9.04

Patch Package Size:  60 Kbytes

Installation Instructions:
        Please review all instructions and the Hewlett-Packard
        SupportLine User Guide or your Hewlett-Packard support terms
        and conditions for precautions, scope of license,
        restrictions, and, limitation of liability and warranties,
        before installing this patch.
        ------------------------------------------------------------
        1. Back up your system before installing a patch.

        2. Login as root.

        3. Copy the patch to the /tmp directory.

        4. Move to the /tmp directory and unshar the patch:

                cd /tmp
                sh PHKL_6783

        5a. For a standalone system, run swinstall to install the
            patch:

                swinstall -x autoreboot=true -x match_target=true \
                        -s /tmp/PHKL_6783.depot

        5b. For a homogeneous NFS Diskless cluster run swcluster on the
            server to install the patch on the server and the clients:

                swcluster -i -b

            This will invoke swcluster in the interactive mode and
            force all clients to be shut down.

            WARNING: All cluster clients must be shut down prior to the
                     patch installation.  Installing the patch while the
                     clients are booted is unsupported and can lead to
                     serious problems.

            The swcluster command will invoke an swinstall session in which
            you must specify:

                alternate root path  -  default is /export/shared_root/OS_700
                source depot path    -  /tmp/PHKL_6783.depot

            To complete the installation, select the patch by choosing
            "Actions -> Match What Target Has" and then "Actions -> Install"
            from the Menubar.

        5c. For a heterogeneous NFS Diskless cluster:

                - run swinstall on the server as in step 5a to install
                  the patch on the cluster server.

                - run swcluster on the server as in step 5b to install
                  the patch on the cluster clients.  The cluster clients
                  must be shut down as described in step 5b.

        By default swinstall will archive the original software in
        /var/adm/sw/patch/PHKL_6783.  If you do not wish to retain a
        copy of the original software, you can create an empty file
        named /var/adm/sw/patch/PATCH_NOSAVE.

        Warning: If this file exists when a patch is installed, the
                 patch cannot be deinstalled.  Please be careful
                 when using this feature.

        It is recommended that you move the PHKL_6783.text file to
        /var/adm/sw/patch for future reference.

        To put this patch on a magnetic tape and install from the
        tape drive, use the command:

                dd if=/tmp/PHKL_6783.depot of=/dev/rmt/0m bs=2k

Special Installation Instructions:  None