Re: [PATCH v2 2/5] selinux: restore the context string on -ESTALE retry

[sashiko-bot@kernel.org]

> From: Christian Göttsche <cgzones@googlemail.com>
> 
> security_context_to_sid_core() retries the conversion when
> sidtab_context_to_sid() returns -ESTALE because a policy reload froze
> the sidtab in the meantime.  The retry passes scontext2 to
> string_to_context_struct() again, but that function mutates its input:
> it replaces the ':' separators with NUL bytes while parsing.  On the
> second pass the user field is followed by a NUL instead of a ':', so the
> parse fails with -EINVAL for any context, including a perfectly valid
> one.
> 
> Without force this makes the caller see -EINVAL for a valid context.
> With force the (pristine) saved copy gets stored as an uninterpreted,
> unmapped context, so a valid context is treated as unlabeled until the
> next policy reload.
> 
> Restore scontext2 from the caller's buffer before retrying, as
> services_convert_context() already does for the same reason.  The
> buffer was allocated by kmemdup_nul() with scontext_len + 1 bytes and
> the parser never writes past the terminating NUL, so copying
> scontext_len bytes restores it exactly.
> 
> Fixes: 9ad6e9cb39c6 ("selinux: fix race between old and new sidtab")
> Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261109153802.76176-5-cgoettsche@seltendoof.de?part=2