> Separate the boot sector analysis to read_boot_sector(). > And add a check for the fs_name field. > Furthermore, add a strict consistency check, because overlapping areas can > cause serious corruption. > > Signed-off-by: Tetsuhiro Kohada <[email protected]>
Reviewed-by: Sungjong Seo <[email protected]> > --- > Changes in v2: > - rebase with patch 'optimize dir-cache' applied Changes in v3: > - add a check for the fs_name field > > fs/exfat/exfat_raw.h | 2 + > fs/exfat/super.c | 97 ++++++++++++++++++++++++-------------------- > 2 files changed, 56 insertions(+), 43 deletions(-) > > diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h index > 07f74190df44..350ce59cc324 100644 > --- a/fs/exfat/exfat_raw.h > +++ b/fs/exfat/exfat_raw.h > @@ -10,11 +10,13 @@ > > #define BOOT_SIGNATURE 0xAA55 > #define EXBOOT_SIGNATURE 0xAA550000 > +#define STR_EXFAT "EXFAT " /* size should be 8 */ > > #define EXFAT_MAX_FILE_LEN 255 > > #define VOL_CLEAN 0x0000 > #define VOL_DIRTY 0x0002 > +#define ERR_MEDIUM 0x0004 > > #define EXFAT_EOF_CLUSTER 0xFFFFFFFFu > #define EXFAT_BAD_CLUSTER 0xFFFFFFF7u > diff --git a/fs/exfat/super.c b/fs/exfat/super.c index > e60d28e73ff0..6a1330be5a9a 100644 > --- a/fs/exfat/super.c > +++ b/fs/exfat/super.c > @@ -366,25 +366,20 @@ static int exfat_read_root(struct inode *inode) > return 0; > } > > -static struct boot_sector *exfat_read_boot_with_logical_sector( > - struct super_block *sb) > +static int exfat_calibrate_blocksize(struct super_block *sb, int > +logical_sect) > { > struct exfat_sb_info *sbi = EXFAT_SB(sb); > - struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh- > >b_data; > - unsigned short logical_sect = 0; > - > - logical_sect = 1 << p_boot->sect_size_bits; > > if (!is_power_of_2(logical_sect) || > logical_sect < 512 || logical_sect > 4096) { > exfat_err(sb, "bogus logical sector size %u", logical_sect); > - return NULL; > + return -EIO; > } > > if (logical_sect < sb->s_blocksize) { > exfat_err(sb, "logical sector size too small for device > (logical sector size = %u)", > logical_sect); > - return NULL; > + return -EIO; > } > > if (logical_sect > sb->s_blocksize) { > @@ -394,24 +389,20 @@ static struct boot_sector > *exfat_read_boot_with_logical_sector( > if (!sb_set_blocksize(sb, logical_sect)) { > exfat_err(sb, "unable to set blocksize %u", > logical_sect); > - return NULL; > + return -EIO; > } > sbi->boot_bh = sb_bread(sb, 0); > if (!sbi->boot_bh) { > exfat_err(sb, "unable to read boot sector (logical > sector size = %lu)", > sb->s_blocksize); > - return NULL; > + return -EIO; > } > - > - p_boot = (struct boot_sector *)sbi->boot_bh->b_data; > } > - return p_boot; > + return 0; > } > > -/* mount the file system volume */ > -static int __exfat_fill_super(struct super_block *sb) > +static int exfat_read_boot_sector(struct super_block *sb) > { > - int ret; > struct boot_sector *p_boot; > struct exfat_sb_info *sbi = EXFAT_SB(sb); > > @@ -424,51 +415,41 @@ static int __exfat_fill_super(struct super_block *sb) > exfat_err(sb, "unable to read boot sector"); > return -EIO; > } > - > - /* PRB is read */ > p_boot = (struct boot_sector *)sbi->boot_bh->b_data; > > /* check the validity of BOOT */ > if (le16_to_cpu((p_boot->signature)) != BOOT_SIGNATURE) { > exfat_err(sb, "invalid boot record signature"); > - ret = -EINVAL; > - goto free_bh; > + return -EINVAL; > } > > - > - /* check logical sector size */ > - p_boot = exfat_read_boot_with_logical_sector(sb); > - if (!p_boot) { > - ret = -EIO; > - goto free_bh; > + if (memcmp(p_boot->fs_name, STR_EXFAT, BOOTSEC_FS_NAME_LEN)) { > + exfat_err(sb, "invalid fs_name"); /* fs_name may unprintable > */ > + return -EINVAL; > } > > /* > - * res_zero field must be filled with zero to prevent mounting > + * must_be_zero field must be filled with zero to prevent mounting > * from FAT volume. > */ > - if (memchr_inv(p_boot->must_be_zero, 0, > - sizeof(p_boot->must_be_zero))) { > - ret = -EINVAL; > - goto free_bh; > - } > + if (memchr_inv(p_boot->must_be_zero, 0, sizeof(p_boot- > >must_be_zero))) > + return -EINVAL; > > - p_boot = (struct boot_sector *)p_boot; > - if (!p_boot->num_fats) { > + if (p_boot->num_fats != 1 && p_boot->num_fats != 2) { > exfat_err(sb, "bogus number of FAT structure"); > - ret = -EINVAL; > - goto free_bh; > + return -EINVAL; > } > > sbi->sect_per_clus = 1 << p_boot->sect_per_clus_bits; > sbi->sect_per_clus_bits = p_boot->sect_per_clus_bits; > - sbi->cluster_size_bits = sbi->sect_per_clus_bits + sb- > >s_blocksize_bits; > + sbi->cluster_size_bits = p_boot->sect_per_clus_bits + > + p_boot->sect_size_bits; > sbi->cluster_size = 1 << sbi->cluster_size_bits; > sbi->num_FAT_sectors = le32_to_cpu(p_boot->fat_length); > sbi->FAT1_start_sector = le32_to_cpu(p_boot->fat_offset); > - sbi->FAT2_start_sector = p_boot->num_fats == 1 ? > - sbi->FAT1_start_sector : > - sbi->FAT1_start_sector + sbi->num_FAT_sectors; > + sbi->FAT2_start_sector = le32_to_cpu(p_boot->fat_offset); > + if (p_boot->num_fats == 2) > + sbi->FAT2_start_sector += sbi->num_FAT_sectors; > sbi->data_start_sector = le32_to_cpu(p_boot->clu_offset); > sbi->num_sectors = le64_to_cpu(p_boot->vol_length); > /* because the cluster index starts with 2 */ @@ -483,15 +464,45 @@ > static int __exfat_fill_super(struct super_block *sb) > sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER; > sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED; > > - if (le16_to_cpu(p_boot->vol_flags) & VOL_DIRTY) { > - sbi->vol_flag |= VOL_DIRTY; > - exfat_warn(sb, "Volume was not properly unmounted. Some data > may be corrupt. Please run fsck."); > + /* check consistencies */ > + if (sbi->num_FAT_sectors << p_boot->sect_size_bits < > + sbi->num_clusters * 4) { > + exfat_err(sb, "bogus fat length"); > + return -EINVAL; > + } > + if (sbi->data_start_sector < > + sbi->FAT1_start_sector + sbi->num_FAT_sectors * p_boot->num_fats) > { > + exfat_err(sb, "bogus data start sector"); > + return -EINVAL; > } > + if (sbi->vol_flag & VOL_DIRTY) > + exfat_warn(sb, "Volume was not properly unmounted. Some data > may be corrupt. Please run fsck."); > + if (sbi->vol_flag & ERR_MEDIUM) > + exfat_warn(sb, "Medium has reported failures. Some data may > be > +lost."); > > /* exFAT file size is limited by a disk volume size */ > sb->s_maxbytes = (u64)(sbi->num_clusters - EXFAT_RESERVED_CLUSTERS) > << > sbi->cluster_size_bits; > > + /* check logical sector size */ > + if (exfat_calibrate_blocksize(sb, 1 << p_boot->sect_size_bits)) > + return -EIO; > + > + return 0; > +} > + > +/* mount the file system volume */ > +static int __exfat_fill_super(struct super_block *sb) { > + int ret; > + struct exfat_sb_info *sbi = EXFAT_SB(sb); > + > + ret = exfat_read_boot_sector(sb); > + if (ret) { > + exfat_err(sb, "failed to read boot sector"); > + goto free_bh; > + } > + > ret = exfat_create_upcase_table(sb); > if (ret) { > exfat_err(sb, "failed to load upcase table"); > -- > 2.25.1
