Re: [PATCH] vfs: fix IMA lockdep circular locking dependency
From: Linus Torvalds
Date: Tue May 15 2012 - 14:41:27 EST
On Tue, May 15, 2012 at 10:19 AM, Linus Torvalds
> - move the whole call to security_file_mmap() to outside the
> mmap_sem, and test the *suggested* address (which is not the same as
> the final address)
Actually, I think I have a simpler approach.
We already actually have two *different* security_file_mmap() calls:
it's just that currently the difference is shown by the last argument
to the function ("addr_only").
Which is totally static by call-site.
And the ones that have addr_only set are all inside the mmap_sem region.
So here's my new suggestion, which avoids the semantic changes: let's
just split that "security_file_mmap()" call into two. One that checks
the file, and one that checks the address.
And we'll continue to check the address within the mmap_sem region,
but nobody will care, because that one doesn't need any other locking.
So we'll just split the file check - along with the ima_file_mmap() -
into the "security_mmap_file()" function (no "addr_only" argument),
and move that outside the lock.
And then the address-only check (let's call it "security_mmap_addr()")
we leave at the place we *currently* do our security_file_mmap()
check, along with (obviously) the calls that currently have
"addr_only=1" and only give the address anyway).
That cleans up the whole nasty piece of crap calling convention too,
getting rid of idiotic unreadable code like
ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
and replacing it with
ret = security_mmap_addr(new_addr);
which actually shows what it is doing.
Hmm? That looks like a fairly mechanical conversion, and we could
start with Mimi's patch that already splits it up that way (except it
calls "security_mmap_file()" ima_file_mmap() and doesn't call the LSM
function pointer there)
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