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fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions

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[ Upstream commit 17457784004c84178798432a029ab20e14f728b1 ]

Some architectures do not populate the entire range categorised by
KCORE_TEXT, so we must ensure that the kernel address we read from is
valid.

Unfortunately there is no solution currently available to do so with a
purely iterator solution so reinstate the bounce buffer in this instance
so we can use copy_from_kernel_nofault() in order to avoid page faults
when regions are unmapped.

This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid
bounce buffer for ktext data"), reinstating the bounce buffer, but adapts
the code to continue to use an iterator.

[lstoakes@gmail.com: correct comment to be strictly correct about reasoning]
  Link: https://lkml.kernel.org/r/525a3f14-74fa-4c22-9fca-9dab4de8a0c3@lucifer.local
Link: https://lkml.kernel.org/r/20230731215021.70911-1-lstoakes@gmail.com
Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data")
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava
Tested-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Will Deacon <will@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 3d5854d75e31 ("fs/proc/kcore.c: allow translation of physical memory addresses")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Lorenzo Stoakes 2023-07-31 22:50:21 +01:00 committed by Greg Kroah-Hartman
parent 28327558b2
commit 7f9b58a646
1 changed files with 14 additions and 3 deletions
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17
fs/proc/kcore.c
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@ -543,10 +543,21 @@ read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
case KCORE_VMEMMAP:
case KCORE_TEXT:
/*
* We use _copy_to_iter() to bypass usermode hardening
* which would otherwise prevent this operation.
* Sadly we must use a bounce buffer here to be able to
* make use of copy_from_kernel_nofault(), as these
* memory regions might not always be mapped on all
* architectures.
*/
if (_copy_to_iter((char *)start, tsz, iter) != tsz) {
if (copy_from_kernel_nofault(buf, (void *)start, tsz)) {
if (iov_iter_zero(tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
/*
* We know the bounce buffer is safe to copy from, so
* use _copy_to_iter() directly.
*/
} else if (_copy_to_iter(buf, tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}