Date: Tue, 10 Jul 2018 02:46:31 +0000 (UTC) From: Xin LI <delphij@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r336158 - stable/11/sbin/fsck_msdosfs Message-ID: <201807100246.w6A2kVh5035493@repo.freebsd.org>
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Author: delphij Date: Tue Jul 10 02:46:31 2018 New Revision: 336158 URL: https://svnweb.freebsd.org/changeset/base/336158 Log: MFC r335655: Fix division by zero when reading boot block by postponing division until it is necessary and after we validated bytes per sector is non- zero. Obtained from: Android https://android-review.googlesource.com/c/platform/external/fsck_msdos/+/36362 Modified: stable/11/sbin/fsck_msdosfs/boot.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sbin/fsck_msdosfs/boot.c ============================================================================== --- stable/11/sbin/fsck_msdosfs/boot.c Tue Jul 10 02:43:22 2018 (r336157) +++ stable/11/sbin/fsck_msdosfs/boot.c Tue Jul 10 02:46:31 2018 (r336158) @@ -178,12 +178,8 @@ readboot(int dosfs, struct bootblock *boot) /* Check backup bpbFSInfo? XXX */ } - boot->ClusterOffset = (boot->bpbRootDirEnts * 32 + - boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + - boot->bpbResSectors + boot->bpbFATs * boot->FATsecs - - CLUST_FIRST * boot->bpbSecPerClust; - - if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0) { + if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0 || + boot->bpbBytesPerSec == 0) { pfatal("Invalid sector size: %u", boot->bpbBytesPerSec); return FSFATAL; } @@ -196,6 +192,10 @@ readboot(int dosfs, struct bootblock *boot) boot->NumSectors = boot->bpbSectors; } else boot->NumSectors = boot->bpbHugeSectors; + boot->ClusterOffset = (boot->bpbRootDirEnts * 32 + + boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + + boot->bpbResSectors + boot->bpbFATs * boot->FATsecs - + CLUST_FIRST * boot->bpbSecPerClust; boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->bpbSecPerClust;
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