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Lecture typo fixes and cscope optimization #19

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merged 3 commits into from
Mar 4, 2018
Merged

Lecture typo fixes and cscope optimization #19

merged 3 commits into from
Mar 4, 2018

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Sergiu121
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For more info into the compiled source option check this link: https://patchwork.kernel.org/patch/1834701/

tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 2, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
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Thanks for the fixes. Overall looks good there are just minor nits I would like you to fix, please see my inline comments.

Documentation/teaching/labs/introduction.rst Outdated
@@ -69,6 +69,13 @@ architecture through the ARCH variable is optional but recommended;
otherwise, some architecture dependent functions will appear multiple
times in the database.

You can build the cscope database with the command :command:`make ARCH
= x86 COMPILED_SOURCE = 1 cscope`. This way, the cscope database will
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Please remove the spaces before and after =

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I followed the pattern from the above paragraph, where spaces are used. Should I delete the spaces from there too?

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yes

Documentation/teaching/lectures/intro.rst Outdated
a particular user process. The kernel space is accessed protected so
that user applications can not access it directly, while user space
can be directly accessed from code running in kernel mode.
reserved to the kernel while user space is the memory area
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This looks like newlines changes only, please revert this hunk.

Documentation/teaching/lectures/syscalls.rst Outdated
crafted:

.. slide:: Marking kernel code that accesses user space
:inline-contents: True
:level: 2

* The exact instructions that access user space are recorded in a
table (exception table)
* The exact instructions that access user space are recorded
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Same here, looks like newlines changes only.

Documentation/teaching/lectures/syscalls.rst Outdated
@@ -372,7 +372,8 @@ With VDSO the system call interface is decided by the kernel:
:level: 2

* a stream of instructions to issue the system call is generated by
the kernel in a special memory area (as en ELF .so)
the kernel in a special memory area (in memory it is formated as
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Maybe "(formatted as an ELF shared object)" is better? Since it is in memory, it is not a file :)

tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 3, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
6c7de28
tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 3, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
d280119
tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 3, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
06d54fa
tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 3, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
d2e1ee4
tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 3, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
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Sergiu121 commented Mar 4, 2018 •
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@i have made the changes. Please review the pull request again.

tavip pushed a commit to linux-kernel-labs/linux-kernel-labs.github.io that referenced this pull request Mar 4, 2018
Publish pull/19 (built from linux-kernel-labs/linux#19)
49591e1
@dbaluta dbaluta merged commit e23b879 into linux-kernel-labs:master Mar 4, 2018
dbaluta pushed a commit to dbaluta/linux that referenced this pull request Nov 7, 2019
@piastry
CIFS: Fix retry mid list corruption on reconnects
abe5707 
When the client hits reconnect it iterates over the mid
pending queue marking entries for retry and moving them
to a temporary list to issue callbacks later without holding
GlobalMid_Lock. In the same time there is no guarantee that
mids can't be removed from the temporary list or even
freed completely by another thread. It may cause a temporary
list corruption:

[  430.454897] list_del corruption. prev->next should be ffff98d3a8f316c0, but was 2e885cb266355469
[  430.464668] ------------[ cut here ]------------
[  430.466569] kernel BUG at lib/list_debug.c:51!
[  430.468476] invalid opcode: 0000 [#1] SMP PTI
[  430.470286] CPU: 0 PID: 13267 Comm: cifsd Kdump: loaded Not tainted 5.4.0-rc3+ linux-kernel-labs#19
[  430.473472] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[  430.475872] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55
...
[  430.510426] Call Trace:
[  430.511500]  cifs_reconnect+0x25e/0x610 [cifs]
[  430.513350]  cifs_readv_from_socket+0x220/0x250 [cifs]
[  430.515464]  cifs_read_from_socket+0x4a/0x70 [cifs]
[  430.517452]  ? try_to_wake_up+0x212/0x650
[  430.519122]  ? cifs_small_buf_get+0x16/0x30 [cifs]
[  430.521086]  ? allocate_buffers+0x66/0x120 [cifs]
[  430.523019]  cifs_demultiplex_thread+0xdc/0xc30 [cifs]
[  430.525116]  kthread+0xfb/0x130
[  430.526421]  ? cifs_handle_standard+0x190/0x190 [cifs]
[  430.528514]  ? kthread_park+0x90/0x90
[  430.530019]  ret_from_fork+0x35/0x40

Fix this by obtaining extra references for mids being retried
and marking them as MID_DELETED which indicates that such a mid
has been dequeued from the pending list.

Also move mid cleanup logic from DeleteMidQEntry to
_cifs_mid_q_entry_release which is called when the last reference
to a particular mid is put. This allows to avoid any use-after-free
of response buffers.

The patch needs to be backported to stable kernels. A stable tag
is not mentioned below because the patch doesn't apply cleanly
to any actively maintained stable kernel.

Reviewed-by: Ronnie Sahlberg <[email protected]>
Reviewed-and-tested-by: David Wysochanski <[email protected]>
Signed-off-by: Pavel Shilovsky <[email protected]>
Signed-off-by: Steve French <[email protected]>
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@Sergiu121 @dbaluta @tavip