Messages in this thread Patch in this message | | | Date | Wed, 12 Apr 2023 09:25:17 -0700 | From | Josh Poimboeuf <> | Subject | Re: linux-next: build warnings after merge of the block tree |
| |
On Wed, Apr 12, 2023 at 01:44:00PM +0200, Peter Zijlstra wrote: > On Tue, Apr 11, 2023 at 05:14:00PM -0700, Josh Poimboeuf wrote: > > > Peter, what do you think, should we make track uaccess state across > > function boundaries? > > So IIRC the goal was to explicitly dis-allow that. You want minimal code > executed with STAC and hence disallow calling stuff.
I guess I was wondering if we could make an exception for calls to static IPA-optimized functions, so we wouldn't have to scramble to "fix" compiler optimizations.
But for now, yeah let's just keep it simple.
Jens, can you confirm this works? I added __noclone instead of removing static.
---8<---
From: Josh Poimboeuf <jpoimboe@kernel.org> Subject: [PATCH] iov_iter: Mark copy_compat_iovec_from_user() noinline
After commit 6376ce56feb6 ("iov_iter: import single vector iovecs as ITER_UBUF"), GCC does an inter-procedural compiler optimization which moves the user_access_begin() out of copy_compat_iovec_from_user() and into its callers:
lib/iov_iter.o: warning: objtool: .altinstr_replacement+0x0: redundant UACCESS disable lib/iov_iter.o: warning: objtool: iovec_from_user.part.0+0xc7: call to copy_compat_iovec_from_user.part.0() with UACCESS enabled lib/iov_iter.o: warning: objtool: __import_iovec+0x21d: call to copy_compat_iovec_from_user.part.0() with UACCESS enabled
Enforce the "no UACCESS enable across function boundaries" rule by disabling cloning for copy_compat_iovec_from_user().
Fixes: 6376ce56feb6 ("iov_iter: import single vector iovecs as ITER_UBUF") Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> https://lkml.kernel.org/lkml/20230327120017.6bb826d7@canb.auug.org.au Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- lib/iov_iter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 274014e4eafe..48aa9fd99267 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1698,7 +1698,7 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags) } EXPORT_SYMBOL(dup_iter); -static int copy_compat_iovec_from_user(struct iovec *iov, +static __noclone int copy_compat_iovec_from_user(struct iovec *iov, const struct iovec __user *uvec, unsigned long nr_segs) { const struct compat_iovec __user *uiov = -- 2.39.2
| |