mm: enforce min addr even if capable() in expand_downwards()
commit 0a1d52994d440e21def1c2174932410b4f2a98a1 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>
This commit is contained in:
parent
7404c65cac
commit
40952b6a64
1 changed files with 3 additions and 4 deletions
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@ -2294,12 +2294,11 @@ int expand_downwards(struct vm_area_struct *vma,
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struct mm_struct *mm = vma->vm_mm;
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struct vm_area_struct *prev;
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unsigned long gap_addr;
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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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gap_addr = address - stack_guard_gap;
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