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dax: fix PMD faults on zero-length files
commit957ac8c421
upstream. PMD faults on a zero length file on a file system mounted with -o dax will not generate SIGBUS as expected. fd = open(...O_TRUNC); addr = mmap(NULL, 2*1024*1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); *addr = 'a'; <expect SIGBUS> The problem is this code in dax_iomap_pmd_fault: max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT; If the inode size is zero, we end up with a max_pgoff that is way larger than 0. :) Fix it by using DIV_ROUND_UP, as is done elsewhere in the kernel. I tested this with some simple test code that ensured that SIGBUS was received where expected. Fixes:642261ac99
("dax: add struct iomap based DAX PMD support") Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
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commit
c21261e631
1 changed files with 3 additions and 3 deletions
6
fs/dax.c
6
fs/dax.c
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@ -1327,7 +1327,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
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* this is a reliable test.
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*/
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pgoff = linear_page_index(vma, pmd_addr);
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max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
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max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
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trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
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@ -1351,13 +1351,13 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
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if ((pmd_addr + PMD_SIZE) > vma->vm_end)
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goto fallback;
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if (pgoff > max_pgoff) {
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if (pgoff >= max_pgoff) {
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result = VM_FAULT_SIGBUS;
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goto out;
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}
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/* If the PMD would extend beyond the file size */
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if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
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if ((pgoff | PG_PMD_COLOUR) >= max_pgoff)
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goto fallback;
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/*
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