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SubjectRe: [PATCH] aio: Convert ioctx_table to XArray
Matthew Wilcox <> writes:

> This custom resizing array was vulnerable to a Spectre attack (speculating
> off the end of an array to a user-controlled offset). The XArray is
> not vulnerable to Spectre as it always masks its lookups to be within
> the bounds of the array.

I'm not a big fan of completely re-writing the code to fix this. Isn't
the below patch sufficient?


diff --git a/fs/aio.c b/fs/aio.c
index 97f983592925..9402ae0b63d5 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1038,6 +1038,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
if (!table || id >= table->nr)
goto out;

+ id = array_index_nospec(index, table->nr);
ctx = rcu_dereference(table->table[id]);
if (ctx && ctx->user_id == ctx_id) {
if (percpu_ref_tryget_live(&ctx->users))
 \ /
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