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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2018-08-21 21:59:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 10:52:50 -0700
commit0afa9626667c3659ef8bd82d42a11e39fedf235c (patch)
tree9b5c96147d7eb18dc6d6b148e2f02c76b8ef9053 /fs/fat
parentf663b5b38fffeb31841f8bfaf0ef87a445b0ffee (diff)
downloadlinux-0afa9626667c3659ef8bd82d42a11e39fedf235c.tar.bz2
fat: validate ->i_start before using
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>
Diffstat (limited to 'fs/fat')
-rw-r--r--fs/fat/cache.c19
-rw-r--r--fs/fat/fat.h5
-rw-r--r--fs/fat/fatent.c6
3 files changed, 20 insertions, 10 deletions
diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index e9bed49df6b7..78d501c1fb65 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -225,7 +225,8 @@ static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
{
struct super_block *sb = inode->i_sb;
- const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ const int limit = sb->s_maxbytes >> sbi->cluster_bits;
struct fat_entry fatent;
struct fat_cache_id cid;
int nr;
@@ -234,6 +235,12 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
*fclus = 0;
*dclus = MSDOS_I(inode)->i_start;
+ if (!fat_valid_entry(sbi, *dclus)) {
+ fat_fs_error_ratelimit(sb,
+ "%s: invalid start cluster (i_pos %lld, start %08x)",
+ __func__, MSDOS_I(inode)->i_pos, *dclus);
+ return -EIO;
+ }
if (cluster == 0)
return 0;
@@ -250,9 +257,8 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
/* prevent the infinite loop of cluster chain */
if (*fclus > limit) {
fat_fs_error_ratelimit(sb,
- "%s: detected the cluster chain loop"
- " (i_pos %lld)", __func__,
- MSDOS_I(inode)->i_pos);
+ "%s: detected the cluster chain loop (i_pos %lld)",
+ __func__, MSDOS_I(inode)->i_pos);
nr = -EIO;
goto out;
}
@@ -262,9 +268,8 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
goto out;
else if (nr == FAT_ENT_FREE) {
fat_fs_error_ratelimit(sb,
- "%s: invalid cluster chain (i_pos %lld)",
- __func__,
- MSDOS_I(inode)->i_pos);
+ "%s: invalid cluster chain (i_pos %lld)",
+ __func__, MSDOS_I(inode)->i_pos);
nr = -EIO;
goto out;
} else if (nr == FAT_ENT_EOF) {
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 154ae54a6b3a..df84d5710b59 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -348,6 +348,11 @@ static inline void fatent_brelse(struct fat_entry *fatent)
fatent->fat_inode = NULL;
}
+static inline bool fat_valid_entry(struct msdos_sb_info *sbi, int entry)
+{
+ return FAT_START_ENT <= entry && entry < sbi->max_cluster;
+}
+
extern void fat_ent_access_init(struct super_block *sb);
extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent,
int entry);
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 25d43a5e8a4d..defc2168de91 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -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;