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mm/mremap: replace can_modify_mm with can_modify_vma

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Delegate all can_modify checks to the proper places.  Unmap checks are
done in do_unmap (et al).  The source VMA check is done purposefully
before unmapping, to keep the original mseal semantics.

Link: https://lkml.kernel.org/r/20240817-mseal-depessimize-v3-4-d8d2e037df30@gmail.com
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pedro Falcato 2024-08-17 01:18:31 +01:00 committed by Andrew Morton
parent 4a2dd02b09
commit 38075679b5
1 changed files with 6 additions and 26 deletions
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32
mm/mremap.c
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@ -902,19 +902,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
return -ENOMEM;
/*
* In mremap_to().
* Move a VMA to another location, check if src addr is sealed.
*
* Place can_modify_mm here because mremap_to()
* does its own checking for address range, and we only
* check the sealing after passing those checks.
*
* can_modify_mm assumes we have acquired the lock on MM.
*/
if (unlikely(!can_modify_mm(mm, addr, addr + old_len)))
return -EPERM;
if (flags & MREMAP_FIXED) {
/*
* In mremap_to().
@ -1052,6 +1039,12 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
goto out;
}
/* Don't allow remapping vmas when they have already been sealed */
if (!can_modify_vma(vma)) {
ret = -EPERM;
goto out;
}
if (is_vm_hugetlb_page(vma)) {
struct hstate *h __maybe_unused = hstate_vma(vma);
@ -1079,19 +1072,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
goto out;
}
/*
* Below is shrink/expand case (not mremap_to())
* Check if src address is sealed, if so, reject.
* In other words, prevent shrinking or expanding a sealed VMA.
*
* Place can_modify_mm here so we can keep the logic related to
* shrink/expand together.
*/
if (unlikely(!can_modify_mm(mm, addr, addr + old_len))) {
ret = -EPERM;
goto out;
}
/*
* Always allow a shrinking remap: that just unmaps
* the unnecessary pages..