powerpc, mm: Fix mprotect on book3s 32-bit

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commit 78fc63ffa7 upstream.

On 32-bit book3s with hash-MMUs, tlb_flush() was a no-op. This was
unnoticed because all uses until recently were for unmaps, and thus
handled by __tlb_remove_tlb_entry().

After commit 4a18419f71 ("mm/mprotect: use mmu_gather") in kernel 5.19,
tlb_gather_mmu() started being used for mprotect as well. This caused
mprotect to simply not work on these machines:

  int *ptr = mmap(NULL, 4096, PROT_READ|PROT_WRITE,
                  MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
  *ptr = 1; // force HPTE to be created
  mprotect(ptr, 4096, PROT_READ);
  *ptr = 2; // should segfault, but succeeds

Fixed by making tlb_flush() actually flush TLB pages. This finally
agrees with the behaviour of boot3s64's tlb_flush().

Fixes: 4a18419f71 ("mm/mprotect: use mmu_gather")
Cc: stable@vger.kernel.org
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Dave Vasilevsky <dave@vasilevsky.ca>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20251116-vasi-mprotect-g3-v3-1-59a9bd33ba00@vasilevsky.ca
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Dave Vasilevsky 2025-11-16 01:40:46 -05:00 • committed by Greg Kroah-Hartman

parent 3968852076

commit acba48ba51

2 changed files with 13 additions and 1 deletions

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5

arch/powerpc/include/asm/book3s/32/tlbflush.h

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9

arch/powerpc/mm/book3s32/tlb.c

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