Re: Regression: NULL pointer dereference after NFS_V4_2_READ_PLUS (commit 7fd461c47)

[Linux kernel regression tracking (#adding)]

[TLDR: I'm adding this report to the list of tracked Linux kernel
regressions; the text you find below is based on a few templates
paragraphs you might have encountered already in similar form.
See link in footer if these mails annoy you.]

On 07.01.23 16:44, Krzysztof Kozlowski wrote:
> Hi,
> 
> Bisect identified commit 7fd461c47c6c ("NFSv4.2: Change the default
> KConfig value for READ_PLUS") as one leading to NULL pointer exception
> when mounting NFS root on NFSv4 client:
> 
> [   25.739003] systemd[1]: Set hostname to <odroidhc1>.
> [   25.771714] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid
> argument
> [   26.199478] 8<--- cut here ---
> [   26.201366] Unable to handle kernel NULL pointer dereference at
> virtual address 00000004
> ...
> [   26.555522]  mmiocpy from xdr_inline_decode+0xec/0x16c
> [   26.560628]  xdr_inline_decode from nfs4_xdr_dec_read_plus+0x178/0x358
> [   26.567130]  nfs4_xdr_dec_read_plus from call_decode+0x204/0x304
> 
> Full OOPS attached. Full log available here:
> https://krzk.eu/#/builders/21/builds/3901/steps/15/logs/serial0
> 
> Disabling NFS_V4_2_READ_PLUS fixes the issue, so obviously the commit is
> not the cause, but rather making it default caused the regression.
> 
> I did not make the bisect yet which commit introduced it, if every
> config includes NFS_V4_2_READ_PLUS.
> 
> 
> Some details about platform:
> 
> 1. Arch ARM Linux
> 2. exynos_defconfig
> 3. Odroid HC1 board with ARMv7, octa-core (Cortex-A7+A15), Exynos5422 SoC
> 4. systemd, boot up with static IP set in kernel command line
> 5. No swap
> 6. Kernel, DTB and initramfs are downloaded with TFTP
> 7. NFS root (NFS client) mounted from a NFSv4 server

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced 7fd461c47
#regzbot title nfs: NULL pointer dereference since NFS_V4_2_READ_PLUS is
enabled by default
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply and tell me -- ideally
while also telling regzbot about it, as explained by the page listed in
the footer of this mail.

Developers: When fixing the issue, remember to add 'Link:' tags pointing
to the report (the parent of this mail). See page linked in footer for
details.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
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