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fs/adfs: bigdir: calculate and validate directory checkbyte 

When reading a big directory, calculate the validate the directory
checkbyte to ensure that the directory contents are valid.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Russell King 2019-12-09 11:11:08 +00:00 committed by Al Viro
parent aa3d4e0152
commit d79288b4f6
1 changed files with 38 additions and 0 deletions
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38
fs/adfs/dir_fplus.c
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@ -67,6 +67,39 @@ static int adfs_fplus_validate_tail(const struct adfs_bigdirheader *h,
return 0;
}
static u8 adfs_fplus_checkbyte(struct adfs_dir *dir)
{
struct adfs_bigdirheader *h = dir->bighead;
struct adfs_bigdirtail *t = dir->bigtail;
unsigned int end, bs, bi, i;
__le32 *bp;
u32 dircheck;
end = adfs_fplus_offset(h, le32_to_cpu(h->bigdirentries)) +
le32_to_cpu(h->bigdirnamesize);
/* Accumulate the contents of the header, entries and names */
for (dircheck = 0, bi = 0; end; bi++) {
bp = (void *)dir->bhs[bi]->b_data;
bs = dir->bhs[bi]->b_size;
if (bs > end)
bs = end;
for (i = 0; i < bs; i += sizeof(u32))
dircheck = ror32(dircheck, 13) ^ le32_to_cpup(bp++);
end -= bs;
}
/* Accumulate the contents of the tail except for the check byte */
dircheck = ror32(dircheck, 13) ^ le32_to_cpu(t->bigdirendname);
dircheck = ror32(dircheck, 13) ^ t->bigdirendmasseq;
dircheck = ror32(dircheck, 13) ^ t->reserved[0];
dircheck = ror32(dircheck, 13) ^ t->reserved[1];
return dircheck ^ dircheck >> 8 ^ dircheck >> 16 ^ dircheck >> 24;
}
static int adfs_fplus_read(struct super_block *sb, u32 indaddr,
unsigned int size, struct adfs_dir *dir)
{
@ -107,6 +140,11 @@ static int adfs_fplus_read(struct super_block *sb, u32 indaddr,
goto out;
}
if (adfs_fplus_checkbyte(dir) != t->bigdircheckbyte) {
adfs_error(sb, "dir %06x checkbyte mismatch\n", indaddr);
goto out;
}
dir->parent_id = le32_to_cpu(h->bigdirparent);
return 0;