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commit 145ea6f10d42dac0a1e8a6dfb83b273c0acabf5b
parent 4624d6ea1b7fe83f1e36caf4537600414ca833f6
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 13 Sep 2018 18:52:41 -1000

Merge tag 'pstore-v4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore fix from Kees Cook:
 "This fixes a 6 year old pstore bug that everyone just got lucky in
  avoiding, likely due only using page-aligned persistent ram regions:

   - Handle page-vs-byte offset handling between iomap and vmap (Bin Yang)"

* tag 'pstore-v4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore: Fix incorrect persistent ram buffer mapping

Diffstat:
Mfs/pstore/ram_core.c | 17++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c @@ -429,7 +429,12 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size, vaddr = vmap(pages, page_count, VM_MAP, prot); kfree(pages); - return vaddr; + /* + * Since vmap() uses page granularity, we must add the offset + * into the page here, to get the byte granularity address + * into the mapping to represent the actual "start" location. + */ + return vaddr + offset_in_page(start); } static void *persistent_ram_iomap(phys_addr_t start, size_t size, @@ -448,6 +453,11 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size, else va = ioremap_wc(start, size); + /* + * Since request_mem_region() and ioremap() are byte-granularity + * there is no need handle anything special like we do when the + * vmap() case in persistent_ram_vmap() above. + */ return va; } @@ -468,7 +478,7 @@ static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size, return -ENOMEM; } - prz->buffer = prz->vaddr + offset_in_page(start); + prz->buffer = prz->vaddr; prz->buffer_size = size - sizeof(struct persistent_ram_buffer); return 0; @@ -515,7 +525,8 @@ void persistent_ram_free(struct persistent_ram_zone *prz) if (prz->vaddr) { if (pfn_valid(prz->paddr >> PAGE_SHIFT)) { - vunmap(prz->vaddr); + /* We must vunmap() at page-granularity. */ + vunmap(prz->vaddr - offset_in_page(prz->paddr)); } else { iounmap(prz->vaddr); release_mem_region(prz->paddr, prz->size);