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Bug fix to UFS/FFS superblock integrity checks when reading a superblock.

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The tests for number of cylinder groups (fs_ncg), inodes per cylinder
group (fs_ipg), and the size and layout of the cylinder group summary
information (fs_csaddr and fs_cssize) were overly restrictive and
would exclude some valid filesystems. These updates avoid precluding
valid fiesystems while still detecting rogue values that can crash or
hang the kernel.

Reported by: Chuck Silvers
Tested by:   Peter Holm
MFC after:   1 month (with 076002f24d)
Differential Revision: https://reviews.freebsd.org/D35219
This commit is contained in:
Kirk McKusick 2022-07-06 13:28:07 -07:00
parent 2bfd8b5b94
commit f3f5368dfb
1 changed files with 16 additions and 18 deletions
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34
sys/ufs/ffs/ffs_subr.c
View file

@ -330,8 +330,8 @@ readsuper(void *devfd, struct fs **fsp, off_t sblockloc, int isaltsblk,
static int
validate_sblock(struct fs *fs, int isaltsblk)
{
int i, sectorsize;
u_int64_t maxfilesize, minfpg, sizepb;
u_long i, sectorsize, cgnum;
u_int64_t maxfilesize, sizepb;
sectorsize = dbtob(1);
if (fs->fs_magic == FS_UFS2_MAGIC) {
@ -409,7 +409,6 @@ validate_sblock(struct fs *fs, int isaltsblk)
CHK(fs->fs_iblkno, !=, fs->fs_cblkno + fs->fs_frag, %jd);
CHK(fs->fs_dblkno, !=, fs->fs_iblkno + fs->fs_ipg / INOPF(fs), %jd);
CHK(fs->fs_cgsize, >, fs->fs_bsize, %jd);
CHK(fs->fs_csaddr, !=, cgdmin(fs, 0), %jd);
CHK(fs->fs_cssize, !=,
fragroundup(fs, fs->fs_ncg * sizeof(struct csum)), %jd);
CHK(fs->fs_dsize, !=, fs->fs_size - fs->fs_sblkno -
@ -429,24 +428,24 @@ validate_sblock(struct fs *fs, int isaltsblk)
* makes it hard to tightly bound them. So we can only check
* that they are within a broader possible range.
*
* Calculate minfpg, the minimum number of fragments that can be
* in a cylinder group. The value 12289 is calculated in newfs(8)
* when creating the smallest block size UFS version 1 filesystem
* (4096 block size) with no fragments (4096 fragment size). That
* number may be depressed even further for very small filesystems
* since newfs(8) strives to have at least four cylinder groups.
* The size cannot always be accurately determined, but ensure
* that it is consistent with the number of cylinder groups (fs_ncg)
* and the number of fragments per cylinder group (fs_fpg). Ensure
* that the summary information size is correct and that it starts
* and ends in the data area of the same cylinder group.
*/
minfpg = MIN(12289, fs->fs_size / 4);
CHK(fs->fs_ncg, <, 1, %jd);
CHK(fs->fs_ncg, >, (fs->fs_size / minfpg) + 1, %jd);
CHK(fs->fs_fpg, <, minfpg, %jd);
CHK(fs->fs_fpg, >, fs->fs_size, %jd);
CHK(fs->fs_ipg * fs->fs_ncg, >, (((int64_t)(1)) << 32) - INOPB(fs),
%jd);
CHK(fs->fs_ipg, >, fs->fs_fpg, %jd);
CHK(fs->fs_size, <, 8 * fs->fs_frag, %jd);
CHK(fs->fs_size, <=, (fs->fs_ncg - 1) * fs->fs_fpg, %jd);
CHK(fs->fs_size, >, fs->fs_ncg * fs->fs_fpg, %jd);
CHK(fs->fs_cssize, !=,
fragroundup(fs, fs->fs_ncg * sizeof(struct csum)), %jd);
cgnum = dtog(fs, fs->fs_csaddr);
CHK(fs->fs_csaddr, <, cgdmin(fs, cgnum), %jd);
CHK(dtog(fs, fs->fs_csaddr + howmany(fs->fs_cssize, fs->fs_fsize)), >,
cgnum, %jd);
CHK(fs->fs_ipg * fs->fs_ncg, >, (((int64_t)(1)) << 32) - INOPB(fs),
%jd);
/*
* With file system clustering it is possible to allocate
* many contiguous blocks. The kernel variable maxphys defines
@ -466,9 +465,8 @@ validate_sblock(struct fs *fs, int isaltsblk)
* those (mostly 32-bit machines) can (very slowly) handle I/O
* requests that exceed maxphys.
*/
CHK(fs->fs_maxcontig, <, 1, %jd);
CHK(fs->fs_maxcontig, >, MAX(256, maxphys / fs->fs_bsize), %jd);
CHK(fs->fs_maxcontig, <, 0, %jd);
CHK(fs->fs_maxcontig, >, MAX(256, maxphys / fs->fs_bsize), %jd);
CHK2(fs->fs_maxcontig, ==, 0, fs->fs_contigsumsize, !=, 0, %jd);
CHK2(fs->fs_maxcontig, >, 1, fs->fs_contigsumsize, !=,
MIN(fs->fs_maxcontig, FS_MAXCONTIG), %jd);