55 lines
1.7 KiB
Diff
55 lines
1.7 KiB
Diff
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From a41fc323f2ef38f884954a4ba3773a296fd809f8 Mon Sep 17 00:00:00 2001
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From: Andreas Bombe <aeb@debian.org>
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Date: Wed, 11 Mar 2015 21:45:04 +0100
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Subject: [PATCH 12/14] fsck.fat: Fix read beyond end of array on FAT12
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When a FAT12 filesystem contains an odd number of clusters, setting the
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last cluster with set_fat() will trigger a read of the next entry,
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which does not exist in the fat array allocated for this.
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Round up the allocation to an even number of FAT entries for FAT12 so
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that this is fixed without introducing special casing in get_fat().
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Signed-off-by: Andreas Bombe <aeb@debian.org>
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---
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src/fat.c | 14 +++++++++++---
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1 file changed, 11 insertions(+), 3 deletions(-)
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diff --git a/src/fat.c b/src/fat.c
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index 027c586..5a92f56 100644
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--- a/src/fat.c
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+++ b/src/fat.c
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@@ -80,7 +80,7 @@ void get_fat(FAT_ENTRY * entry, void *fat, uint32_t cluster, DOS_FS * fs)
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*/
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void read_fat(DOS_FS * fs)
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{
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- int eff_size;
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+ int eff_size, alloc_size;
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uint32_t i;
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void *first, *second = NULL;
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int first_ok, second_ok;
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@@ -96,10 +96,18 @@ void read_fat(DOS_FS * fs)
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total_num_clusters = fs->clusters + 2UL;
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eff_size = (total_num_clusters * fs->fat_bits + 7) / 8ULL;
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- first = alloc(eff_size);
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+
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+ if (fs->fat_bits != 12)
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+ alloc_size = eff_size;
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+ else
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+ /* round up to an even number of FAT entries to avoid special
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+ * casing the last entry in get_fat() */
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+ alloc_size = (total_num_clusters * 12 + 23) / 24 * 3;
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+
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+ first = alloc(alloc_size);
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fs_read(fs->fat_start, eff_size, first);
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if (fs->nfats > 1) {
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- second = alloc(eff_size);
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+ second = alloc(alloc_size);
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fs_read(fs->fat_start + fs->fat_size, eff_size, second);
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}
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if (second && memcmp(first, second, eff_size) != 0) {
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--
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1.9.1
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