Messages in this thread Patch in this message | | | From | Jeff Moyer <> | Subject | Re: [PATCH] aio: Convert ioctx_table to XArray | Date | Thu, 06 Dec 2018 17:26:33 -0500 |
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Jeff Moyer <jmoyer@redhat.com> writes:
> Matthew Wilcox <willy@infradead.org> 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?
Too quick on the draw. Here's a patch that compiles. ;-)
Cheers, Jeff
diff --git a/fs/aio.c b/fs/aio.c index 97f983592925..aac9659381d2 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -45,6 +45,7 @@ #include <asm/kmap_types.h> #include <linux/uaccess.h> +#include <linux/nospec.h> #include "internal.h" @@ -1038,6 +1039,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id) if (!table || id >= table->nr) goto out; + id = array_index_nospec(id, 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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