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mm/mremap: fix regression in vrm->new_addr check

Commit 3215eaceca87 ("mm/mremap: refactor initial parameter sanity
checks") moved the sanity check for vrm->new_addr from mremap_to() to
check_mremap_params().

However, this caused a regression as vrm->new_addr is now checked even
when MREMAP_FIXED and MREMAP_DONTUNMAP flags are not specified. In this
case, vrm->new_addr can be garbage and create unexpected failures.

Fix this by moving the new_addr check after the vrm_implies_new_addr()
guard. This ensures that the new_addr is only checked when the user has
specified one explicitly.

Link: https://lkml.kernel.org/r/20250828142657.770502-1-cmllamas@google.com
Fixes: 3215eaceca87 ("mm/mremap: refactor initial parameter sanity checks")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Carlos Llamas <cmllamas@google.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

authored by

Carlos Llamas and committed by
Andrew Morton 78d2d32f 7989fdce

+6 -3
+6 -3
mm/mremap.c
··· 1774 1774 if (!vrm->new_len) 1775 1775 return -EINVAL; 1776 1776 1777 - /* Is the new length or address silly? */ 1778 - if (vrm->new_len > TASK_SIZE || 1779 - vrm->new_addr > TASK_SIZE - vrm->new_len) 1777 + /* Is the new length silly? */ 1778 + if (vrm->new_len > TASK_SIZE) 1780 1779 return -EINVAL; 1781 1780 1782 1781 /* Remainder of checks are for cases with specific new_addr. */ 1783 1782 if (!vrm_implies_new_addr(vrm)) 1784 1783 return 0; 1784 + 1785 + /* Is the new address silly? */ 1786 + if (vrm->new_addr > TASK_SIZE - vrm->new_len) 1787 + return -EINVAL; 1785 1788 1786 1789 /* The new address must be page-aligned. */ 1787 1790 if (offset_in_page(vrm->new_addr))