Re: Patch "PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter" has been added to the 4.20-stable tree

[Greg KH]

On Thu, Feb 21, 2019 at 12:43:20AM -0500, Sasha Levin wrote:
> This is a note to let you know that I've just added the patch titled
> 
>     PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter
> 
> to the 4.20-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      pci-fix-__initdata-issue-with-pci-disable_acs_redir-.patch
> and it can be found in the queue-4.20 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@xxxxxxxxxxxxxxx> know about it.
> 
> 
> 
> commit 44557eb5390967bb678394cfbcef5df39bfa751e
> Author: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Date:   Thu Jan 17 08:46:34 2019 -0600
> 
>     PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter
>     
>     [ Upstream commit d2fd6e81912a665993b24dcdc1c1384a42a54f7e ]
>     
>     The disable_acs_redir parameter stores a pointer to the string passed to
>     pci_setup().  However, the string passed to PCI setup is actually a
>     temporary copy allocated in static __initdata memory.  After init, once the
>     memory is freed, it is no longer valid to reference this pointer.
>     
>     This bug was noticed in v5.0-rc1 after a change in commit c5eb1190074c
>     ("PCI / PM: Allow runtime PM without callback functions") caused
>     pci_disable_acs_redir() to be called during shutdown which manifested
>     as an unable to handle kernel paging request at:
>     
>       RIP: 0010:pci_enable_acs+0x3f/0x1e0
>       Call Trace:
>          pci_restore_state.part.44+0x159/0x3c0
>          pci_restore_standard_config+0x33/0x40
>          pci_pm_runtime_resume+0x2b/0xd0
>          ? pci_restore_standard_config+0x40/0x40
>          __rpm_callback+0xbc/0x1b0
>          rpm_callback+0x1f/0x70
>          ? pci_restore_standard_config+0x40/0x40
>           rpm_resume+0x4f9/0x710
>          ? pci_conf1_read+0xb6/0xf0
>          ? pci_conf1_write+0xb2/0xe0
>          __pm_runtime_resume+0x47/0x70
>          pci_device_shutdown+0x1e/0x60
>          device_shutdown+0x14a/0x1f0
>          kernel_restart+0xe/0x50
>          __do_sys_reboot+0x1ee/0x210
>          ? __fput+0x144/0x1d0
>          do_writev+0x5e/0xf0
>          ? do_writev+0x5e/0xf0
>          do_syscall_64+0x48/0xf0
>          entry_SYSCALL_64_after_hwframe+0x44/0xa9
>     
>     It was also likely possible to trigger this bug when hotplugging PCI
>     devices.
>     
>     To fix this, instead of storing a pointer, we use kstrdup() to copy the
>     disable_acs_redir_param to its own buffer which will never be freed.
>     
>     Fixes: aaca43fda742 ("PCI: Add "pci=disable_acs_redir=" parameter for peer-to-peer support")

According to this tag it is needed in 4.19.y as well...

now added there.

greg k-h