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mm: enforce min addr even if capable() in expand_downwards()
commit0a1d52994d
upstream. security_mmap_addr() does a capability check with current_cred(), but we can reach this code from contexts like a VFS write handler where current_cred() must not be used. This can be abused on systems without SMAP to make NULL pointer dereferences exploitable again. Fixes:8869477a49
("security: protect from stack expansion into low vm addresses") Cc: stable@kernel.org Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 3 additions and 4 deletions
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@ -2348,12 +2348,11 @@ int expand_downwards(struct vm_area_struct *vma,
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{
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struct mm_struct *mm = vma->vm_mm;
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struct vm_area_struct *prev;
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int error;
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int error = 0;
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address &= PAGE_MASK;
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error = security_mmap_addr(address);
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if (error)
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return error;
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if (address < mmap_min_addr)
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return -EPERM;
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/* Enforce stack_guard_gap */
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prev = vma->vm_prev;
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