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fat: validate ->i_start before using

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On corrupted FATfs may have invalid ->i_start.  To handle it, this checks
->i_start before using, and return proper error code.

Link: http://lkml.kernel.org/r/87o9f8y1t5.fsf_-_@mail.parknet.co.jp
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Tested-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
OGAWA Hirofumi
2018-08-21 21:59:44 -07:00
committed by Linus Torvalds
parent f663b5b38f
commit 0afa962666
3 changed files with 20 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
fs/fat/fatent.c
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@@ -24,7 +24,7 @@ static void fat12_ent_blocknr(struct super_block *sb, int entry,
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
int bytes = entry + (entry >> 1);
WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
WARN_ON(!fat_valid_entry(sbi, entry));
*offset = bytes & (sb->s_blocksize - 1);
*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}
@@ -34,7 +34,7 @@ static void fat_ent_blocknr(struct super_block *sb, int entry,
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
int bytes = (entry << sbi->fatent_shift);
WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
WARN_ON(!fat_valid_entry(sbi, entry));
*offset = bytes & (sb->s_blocksize - 1);
*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}
@@ -354,7 +354,7 @@ int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
int err, offset;
sector_t blocknr;
if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
if (!fat_valid_entry(sbi, entry)) {
fatent_brelse(fatent);
fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
return -EIO;