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What happens if LoadOption is L"\0" ? #95

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edjee opened this issue Sep 8, 2017 · 2 comments
Closed

What happens if LoadOption is L"\0" ? #95

edjee opened this issue Sep 8, 2017 · 2 comments

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@edjee
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edjee commented Sep 8, 2017

shim/shim.c

Line 2531 in e06765a

UINTN strings = count_ucs2_strings(li->LoadOptions,

Hi @vathpela , may I ask about the function "set_second_stage" in shim.c ?

If the LoadOption data happens to be L"\0" , what's the expected results?
I found that the function "count_ucs2_strings" returns 1, when the input is L"\0".

In such a case, do we want to fall back to DEFAULT_LOADER? Or halt?
@edjee
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edjee commented Sep 11, 2017

To me it's strange that count_ucs2_strings() returns 1 for the input L"\0".
Is that an expected behavior? Shouldn't it return 0?

@vathpela
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vathpela commented Mar 6, 2018

L"\0" is one string of length 0. That looks right to me.
I think we want DEFAULT_LOADER in this case.

vathpela added a commit that referenced this issue Mar 6, 2018
@vathpela
shim: Ignore UEFI LoadOptions that are just NUL characters.
6c8d08c 
I don't know when or why we ever see this, but it's easy enough to
avoid.

Resolves github issue #95

Signed-off-by: Peter Jones <pjones@redhat.com>
@vathpela vathpela closed this as completed Mar 6, 2018
frozencemetery added a commit to frozencemetery/shim that referenced this issue Aug 23, 2022
@frozencemetery
Discard load-options that start with a NUL
9b2979b 
In 6c8d08c ("shim: Ignore UEFI
LoadOptions that are just NUL characters."), a check was added to
discard load options that are entirely NUL.  We now see some firmwares
that start LoadOptions with a NUL, and then follow it with garbage (path
to directory containing loaders).  Widen the check to just discard
anything that starts with a NUL.

Resolves: rhboot#490
Related: rhboot#95
See-also: https://bugzilla.redhat.com/show_bug.cgi?id=2113005
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
@frozencemetery frozencemetery mentioned this issue Aug 23, 2022
Merged
frozencemetery added a commit to frozencemetery/shim that referenced this issue Aug 25, 2022
@frozencemetery
Discard load-options that start with a NUL
72cd577 
In 6c8d08c ("shim: Ignore UEFI
LoadOptions that are just NUL characters."), a check was added to
discard load options that are entirely NUL.  We now see some firmwares
that start LoadOptions with a NUL, and then follow it with garbage (path
to directory containing loaders).  Widen the check to just discard
anything that starts with a NUL.

Resolves: rhboot#490
Related: rhboot#95
See-also: https://bugzilla.redhat.com/show_bug.cgi?id=2113005
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
vathpela pushed a commit that referenced this issue Sep 1, 2022
@frozencemetery @vathpela
Discard load-options that start with a NUL
14d6339 
In 6c8d08c ("shim: Ignore UEFI
LoadOptions that are just NUL characters."), a check was added to
discard load options that are entirely NUL.  We now see some firmwares
that start LoadOptions with a NUL, and then follow it with garbage (path
to directory containing loaders).  Widen the check to just discard
anything that starts with a NUL.

Resolves: #490
Related: #95
See-also: https://bugzilla.redhat.com/show_bug.cgi?id=2113005
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
brianredbeard pushed a commit to brianredbeard/redhat-efi-boot-shim that referenced this issue Feb 22, 2024
@frozencemetery @brianredbeard
Discard load-options that start with a NUL
f0d144c 
In 6c8d08c ("shim: Ignore UEFI
LoadOptions that are just NUL characters."), a check was added to
discard load options that are entirely NUL.  We now see some firmwares
that start LoadOptions with a NUL, and then follow it with garbage (path
to directory containing loaders).  Widen the check to just discard
anything that starts with a NUL.

Resolves: rhboot#490
Related: rhboot#95
See-also: https://bugzilla.redhat.com/show_bug.cgi?id=2113005
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
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@vathpela @edjee