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| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2023-02-03 16:28:40 -0500 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-09 16:51:30 -0800 |
| commit | c643e6ebedb435bcf863001f5e69a578f2658055 (patch) | |
| tree | 278d5a939aea70c67e3d379de241d48895e8824b /include/linux/highmem.h | |
| parent | 6f74c0ec2095335158015ce29b708e775b9cea3a (diff) | |
| download | linux-c643e6ebedb435bcf863001f5e69a578f2658055.tar.gz | |
mm: fix memcpy_from_file_folio() integer underflow
If we have a HIGHMEM system with a large folio, 'offset' may be larger
than PAGE_SIZE, and so min_t will cap at 'len' instead of the intended
end-of-page. That can overflow into the next page which is likely to be
unmapped and fault, but could theoretically copy the wrong data.
Link: https://lkml.kernel.org/r/Y919vmSrtAgsf6K3@casper.infradead.org
Fixes: 00cdf76012ab ("mm: add memcpy_from_file_folio()")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/highmem.h')
| -rw-r--r-- | include/linux/highmem.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 348701dae77fd4..b06254e76d99af 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -431,9 +431,10 @@ static inline size_t memcpy_from_file_folio(char *to, struct folio *folio, size_t offset = offset_in_folio(folio, pos); char *from = kmap_local_folio(folio, offset); - if (folio_test_highmem(folio)) + if (folio_test_highmem(folio)) { + offset = offset_in_page(offset); len = min_t(size_t, len, PAGE_SIZE - offset); - else + } else len = min(len, folio_size(folio) - offset); memcpy(to, from, len); |