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minix: Add required sanity checking to minix_check_superblock()

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The fs/minix implementation of the minix filesystem does not currently
support any other value for s_log_zone_size than 0. This is also the
only value supported in util-linux; see mkfs.minix.c line 511. In
addition, this patch adds some sanity checking for the other minix
superblock fields, and moves the minix_blocks_needed() checks for the
zmap and imap also to minix_check_super_block().

This also closes a related syzbot bug report.

Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20251208153947.108343-1-jkoolstra@xs4all.nl
Reviewed-by: Jan Kara <jack@suse.cz>
Reported-by: syzbot+5ad0824204c7bf9b67f2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5ad0824204c7bf9b67f2
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jori Koolstra 2025-12-08 16:39:47 +01:00 committed by Christian Brauner
parent 8f0b4cce44
commit 8c97a6ddc9
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 29 additions and 21 deletions
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50
fs/minix/inode.c
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@ -170,9 +170,37 @@ static int minix_reconfigure(struct fs_context *fc)
static bool minix_check_superblock(struct super_block *sb) static bool minix_check_superblock(struct super_block *sb)
{ {
struct minix_sb_info *sbi = minix_sb(sb); struct minix_sb_info *sbi = minix_sb(sb);
unsigned long block;
if (sbi->s_imap_blocks == 0 || sbi->s_zmap_blocks == 0) if (sbi->s_log_zone_size != 0) {
printk("minix-fs error: zone size must equal block size. "
"s_log_zone_size > 0 is not supported.\n");
return false; return false;
}
if (sbi->s_ninodes < 1 || sbi->s_firstdatazone <= 4 ||
sbi->s_firstdatazone >= sbi->s_nzones)
return false;
/* Apparently minix can create filesystems that allocate more blocks for
* the bitmaps than needed. We simply ignore that, but verify it didn't
* create one with not enough blocks and bail out if so.
*/
block = minix_blocks_needed(sbi->s_ninodes, sb->s_blocksize);
if (sbi->s_imap_blocks < block) {
printk("MINIX-fs: file system does not have enough "
"imap blocks allocated. Refusing to mount.\n");
return false;
}
block = minix_blocks_needed(
(sbi->s_nzones - sbi->s_firstdatazone + 1),
sb->s_blocksize);
if (sbi->s_zmap_blocks < block) {
printk("MINIX-fs: file system does not have enough "
"zmap blocks allocated. Refusing to mount.\n");
return false;
}
/* /*
* s_max_size must not exceed the block mapping limitation. This check * s_max_size must not exceed the block mapping limitation. This check
@ -293,26 +321,6 @@ static int minix_fill_super(struct super_block *s, struct fs_context *fc)
minix_set_bit(0,sbi->s_imap[0]->b_data); minix_set_bit(0,sbi->s_imap[0]->b_data);
minix_set_bit(0,sbi->s_zmap[0]->b_data); minix_set_bit(0,sbi->s_zmap[0]->b_data);
/* Apparently minix can create filesystems that allocate more blocks for
* the bitmaps than needed. We simply ignore that, but verify it didn't
* create one with not enough blocks and bail out if so.
*/
block = minix_blocks_needed(sbi->s_ninodes, s->s_blocksize);
if (sbi->s_imap_blocks < block) {
printk("MINIX-fs: file system does not have enough "
"imap blocks allocated. Refusing to mount.\n");
goto out_no_bitmap;
}
block = minix_blocks_needed(
(sbi->s_nzones - sbi->s_firstdatazone + 1),
s->s_blocksize);
if (sbi->s_zmap_blocks < block) {
printk("MINIX-fs: file system does not have enough "
"zmap blocks allocated. Refusing to mount.\n");
goto out_no_bitmap;
}
/* set up enough so that it can read an inode */ /* set up enough so that it can read an inode */
s->s_op = &minix_sops; s->s_op = &minix_sops;
s->s_time_min = 0; s->s_time_min = 0;