6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
commit a50420c79731fc5cf27ad43719c1091e842a2606 upstream.
flush_cache_vmap() must be called after new vmalloc mappings are installed
in the page table in order to allow architectures to make sure the new
mapping is visible.
It could lead to a panic since on some architectures (like powerpc),
the page table walker could see the wrong pte value and trigger a
spurious page fault that can not be resolved (see commit f1cb8f9beba8
("powerpc/64s/radix: avoid ptesync after set_pte and
ptep_set_access_flags")).
But actually the patch is aiming at riscv: the riscv specification
allows the caching of invalid entries in the TLB, and since we recently
removed the vmalloc page fault handling, we now need to emit a tlb
shootdown whenever a new vmalloc mapping is emitted
(https://lore.kernel.org/linux-riscv/20230725132246.817726-1-alexghiti@xxxxxxxxxxxx/).
That's a temporary solution, there are ways to avoid that :)
Link: https://lkml.kernel.org/r/20230809164633.1556126-1-alexghiti@xxxxxxxxxxxx
Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function")
Reported-by: Dylan Jhong <dylan@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-riscv/ZMytNY2J8iyjbPPy@xxxxxxxxxxxxxxxxxxxx/
Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Reviewed-by: Dylan Jhong <dylan@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2909,6 +2909,10 @@ void *vmap_pfn(unsigned long *pfns, unsi
free_vm_area(area);
return NULL;
}
+
+ flush_cache_vmap((unsigned long)area->addr,
+ (unsigned long)area->addr + count * PAGE_SIZE);
+
return area->addr;
}
EXPORT_SYMBOL_GPL(vmap_pfn);
