From: Theodore Ts'o tytso@mit.edu
[ Upstream commit 5354b2af34064a4579be8bc0e2f15a7b70f14b5f ]
Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen. However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number. In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number. Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device.
For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG. So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL. We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL.
Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it. The results in a next reduction of the compiled text size of ext4 by roughly 2k.
Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230430154311.579720-2-tytso@mit.edu Reported-by: syzbot+e2efa3efc15a1c9e95c3@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=69b28112e098b070f639efb356393af3ffec422... Signed-off-by: Theodore Ts'o tytso@mit.edu Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/balloc.c | 18 ++++++++++++- fs/ext4/ext4.h | 15 ++--------- fs/ext4/ialloc.c | 12 ++++++--- fs/ext4/mballoc.c | 64 +++++++++++++++++++++++++++++++++++++++-------- fs/ext4/super.c | 2 ++ 5 files changed, 82 insertions(+), 29 deletions(-)
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 05ff34e925620..fadcb94e80fa1 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -319,6 +319,22 @@ static ext4_fsblk_t ext4_valid_block_bitmap_padding(struct super_block *sb, return (next_zero_bit < bitmap_size ? next_zero_bit : 0); }
+struct ext4_group_info *ext4_get_group_info(struct super_block *sb, + ext4_group_t group) +{ + struct ext4_group_info **grp_info; + long indexv, indexh; + + if (unlikely(group >= EXT4_SB(sb)->s_groups_count)) { + ext4_error(sb, "invalid group %u", group); + return NULL; + } + indexv = group >> (EXT4_DESC_PER_BLOCK_BITS(sb)); + indexh = group & ((EXT4_DESC_PER_BLOCK(sb)) - 1); + grp_info = sbi_array_rcu_deref(EXT4_SB(sb), s_group_info, indexv); + return grp_info[indexh]; +} + /* * Return the block number which was discovered to be invalid, or 0 if * the block bitmap is valid. @@ -393,7 +409,7 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
if (buffer_verified(bh)) return 0; - if (EXT4_MB_GRP_BBITMAP_CORRUPT(grp)) + if (!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp)) return -EFSCORRUPTED;
ext4_lock_group(sb, block_group); diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 80f0942fa1656..b6e2bb6a736b5 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2699,6 +2699,8 @@ extern void ext4_check_blocks_bitmap(struct super_block *); extern struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb, ext4_group_t block_group, struct buffer_head ** bh); +extern struct ext4_group_info *ext4_get_group_info(struct super_block *sb, + ext4_group_t group); extern int ext4_should_retry_alloc(struct super_block *sb, int *retries);
extern struct buffer_head *ext4_read_block_bitmap_nowait(struct super_block *sb, @@ -3346,19 +3348,6 @@ static inline void ext4_isize_set(struct ext4_inode *raw_inode, loff_t i_size) raw_inode->i_size_high = cpu_to_le32(i_size >> 32); }
-static inline -struct ext4_group_info *ext4_get_group_info(struct super_block *sb, - ext4_group_t group) -{ - struct ext4_group_info **grp_info; - long indexv, indexh; - BUG_ON(group >= EXT4_SB(sb)->s_groups_count); - indexv = group >> (EXT4_DESC_PER_BLOCK_BITS(sb)); - indexh = group & ((EXT4_DESC_PER_BLOCK(sb)) - 1); - grp_info = sbi_array_rcu_deref(EXT4_SB(sb), s_group_info, indexv); - return grp_info[indexh]; -} - /* * Reading s_groups_count requires using smp_rmb() afterwards. See * the locking protocol documented in the comments of ext4_group_add() diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 208b87ce88588..745d781da8915 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -91,7 +91,7 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
if (buffer_verified(bh)) return 0; - if (EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) + if (!grp || EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) return -EFSCORRUPTED;
ext4_lock_group(sb, block_group); @@ -293,7 +293,7 @@ void ext4_free_inode(handle_t *handle, struct inode *inode) } if (!(sbi->s_mount_state & EXT4_FC_REPLAY)) { grp = ext4_get_group_info(sb, block_group); - if (unlikely(EXT4_MB_GRP_IBITMAP_CORRUPT(grp))) { + if (!grp || unlikely(EXT4_MB_GRP_IBITMAP_CORRUPT(grp))) { fatal = -EFSCORRUPTED; goto error_return; } @@ -1048,7 +1048,7 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns, * Skip groups with already-known suspicious inode * tables */ - if (EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) + if (!grp || EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) goto next_group; }
@@ -1186,6 +1186,10 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
if (!(sbi->s_mount_state & EXT4_FC_REPLAY)) { grp = ext4_get_group_info(sb, group); + if (!grp) { + err = -EFSCORRUPTED; + goto out; + } down_read(&grp->alloc_sem); /* * protect vs itable * lazyinit @@ -1529,7 +1533,7 @@ int ext4_init_inode_table(struct super_block *sb, ext4_group_t group, }
gdp = ext4_get_group_desc(sb, group, &group_desc_bh); - if (!gdp) + if (!gdp || !grp) goto out;
/* diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 820804a7afe6e..4cc635633f789 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -745,6 +745,8 @@ static int __mb_check_buddy(struct ext4_buddy *e4b, char *file, MB_CHECK_ASSERT(e4b->bd_info->bb_fragments == fragments);
grp = ext4_get_group_info(sb, e4b->bd_group); + if (!grp) + return NULL; list_for_each(cur, &grp->bb_prealloc_list) { ext4_group_t groupnr; struct ext4_prealloc_space *pa; @@ -1110,9 +1112,9 @@ mb_set_largest_free_order(struct super_block *sb, struct ext4_group_info *grp)
static noinline_for_stack void ext4_mb_generate_buddy(struct super_block *sb, - void *buddy, void *bitmap, ext4_group_t group) + void *buddy, void *bitmap, ext4_group_t group, + struct ext4_group_info *grp) { - struct ext4_group_info *grp = ext4_get_group_info(sb, group); struct ext4_sb_info *sbi = EXT4_SB(sb); ext4_grpblk_t max = EXT4_CLUSTERS_PER_GROUP(sb); ext4_grpblk_t i = 0; @@ -1233,6 +1235,8 @@ static int ext4_mb_init_cache(struct page *page, char *incore, gfp_t gfp) break;
grinfo = ext4_get_group_info(sb, group); + if (!grinfo) + continue; /* * If page is uptodate then we came here after online resize * which added some new uninitialized group info structs, so @@ -1298,6 +1302,10 @@ static int ext4_mb_init_cache(struct page *page, char *incore, gfp_t gfp) group, page->index, i * blocksize); trace_ext4_mb_buddy_bitmap_load(sb, group); grinfo = ext4_get_group_info(sb, group); + if (!grinfo) { + err = -EFSCORRUPTED; + goto out; + } grinfo->bb_fragments = 0; memset(grinfo->bb_counters, 0, sizeof(*grinfo->bb_counters) * @@ -1308,7 +1316,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore, gfp_t gfp) ext4_lock_group(sb, group); /* init the buddy */ memset(data, 0xff, blocksize); - ext4_mb_generate_buddy(sb, data, incore, group); + ext4_mb_generate_buddy(sb, data, incore, group, grinfo); ext4_unlock_group(sb, group); incore = NULL; } else { @@ -1422,6 +1430,9 @@ int ext4_mb_init_group(struct super_block *sb, ext4_group_t group, gfp_t gfp) might_sleep(); mb_debug(sb, "init group %u\n", group); this_grp = ext4_get_group_info(sb, group); + if (!this_grp) + return -EFSCORRUPTED; + /* * This ensures that we don't reinit the buddy cache * page which map to the group from which we are already @@ -1496,6 +1507,8 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group,
blocks_per_page = PAGE_SIZE / sb->s_blocksize; grp = ext4_get_group_info(sb, group); + if (!grp) + return -EFSCORRUPTED;
e4b->bd_blkbits = sb->s_blocksize_bits; e4b->bd_info = grp; @@ -2206,6 +2219,8 @@ int ext4_mb_find_by_goal(struct ext4_allocation_context *ac, struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group); struct ext4_free_extent ex;
+ if (!grp) + return -EFSCORRUPTED; if (!(ac->ac_flags & (EXT4_MB_HINT_TRY_GOAL | EXT4_MB_HINT_GOAL_ONLY))) return 0; if (grp->bb_free == 0) @@ -2430,7 +2445,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
BUG_ON(cr < 0 || cr >= 4);
- if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp))) + if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp) || !grp)) return false;
free = grp->bb_free; @@ -2499,6 +2514,8 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, ext4_grpblk_t free; int ret = 0;
+ if (!grp) + return -EFSCORRUPTED; if (sbi->s_mb_stats) atomic64_inc(&sbi->s_bal_cX_groups_considered[ac->ac_criteria]); if (should_lock) { @@ -2579,7 +2596,7 @@ ext4_group_t ext4_mb_prefetch(struct super_block *sb, ext4_group_t group, * prefetch once, so we avoid getblk() call, which can * be expensive. */ - if (!EXT4_MB_GRP_TEST_AND_SET_READ(grp) && + if (gdp && grp && !EXT4_MB_GRP_TEST_AND_SET_READ(grp) && EXT4_MB_GRP_NEED_INIT(grp) && ext4_free_group_clusters(sb, gdp) > 0 && !(ext4_has_group_desc_csum(sb) && @@ -2623,7 +2640,7 @@ void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group, group--; grp = ext4_get_group_info(sb, group);
- if (EXT4_MB_GRP_NEED_INIT(grp) && + if (grp && gdp && EXT4_MB_GRP_NEED_INIT(grp) && ext4_free_group_clusters(sb, gdp) > 0 && !(ext4_has_group_desc_csum(sb) && (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))) { @@ -2883,6 +2900,8 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v) sizeof(struct ext4_group_info);
grinfo = ext4_get_group_info(sb, group); + if (!grinfo) + return 0; /* Load the group info in memory only if not already loaded. */ if (unlikely(EXT4_MB_GRP_NEED_INIT(grinfo))) { err = ext4_mb_load_buddy(sb, group, &e4b); @@ -2893,7 +2912,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v) buddy_loaded = 1; }
- memcpy(&sg, ext4_get_group_info(sb, group), i); + memcpy(&sg, grinfo, i);
if (buddy_loaded) ext4_mb_unload_buddy(&e4b); @@ -3265,8 +3284,12 @@ static int ext4_mb_init_backend(struct super_block *sb)
err_freebuddy: cachep = get_groupinfo_cache(sb->s_blocksize_bits); - while (i-- > 0) - kmem_cache_free(cachep, ext4_get_group_info(sb, i)); + while (i-- > 0) { + struct ext4_group_info *grp = ext4_get_group_info(sb, i); + + if (grp) + kmem_cache_free(cachep, grp); + } i = sbi->s_group_info_size; rcu_read_lock(); group_info = rcu_dereference(sbi->s_group_info); @@ -3562,6 +3585,8 @@ int ext4_mb_release(struct super_block *sb) for (i = 0; i < ngroups; i++) { cond_resched(); grinfo = ext4_get_group_info(sb, i); + if (!grinfo) + continue; mb_group_bb_bitmap_free(grinfo); ext4_lock_group(sb, i); count = ext4_mb_cleanup_pa(grinfo); @@ -4466,6 +4491,8 @@ static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap, struct ext4_free_data *entry;
grp = ext4_get_group_info(sb, group); + if (!grp) + return; n = rb_first(&(grp->bb_free_root));
while (n) { @@ -4493,6 +4520,9 @@ void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap, int preallocated = 0; int len;
+ if (!grp) + return; + /* all form of preallocation discards first load group, * so the only competing code is preallocation use. * we don't need any locking here @@ -4684,6 +4714,8 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
ei = EXT4_I(ac->ac_inode); grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group); + if (!grp) + return;
pa->pa_obj_lock = &ei->i_prealloc_lock; pa->pa_inode = ac->ac_inode; @@ -4737,6 +4769,8 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac) atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);
grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group); + if (!grp) + return; lg = ac->ac_lg; BUG_ON(lg == NULL);
@@ -4865,6 +4899,8 @@ ext4_mb_discard_group_preallocations(struct super_block *sb, int err; int free = 0;
+ if (!grp) + return 0; mb_debug(sb, "discard preallocation for group %u\n", group); if (list_empty(&grp->bb_prealloc_list)) goto out_dbg; @@ -5102,6 +5138,9 @@ static inline void ext4_mb_show_pa(struct super_block *sb) struct ext4_prealloc_space *pa; ext4_grpblk_t start; struct list_head *cur; + + if (!grp) + continue; ext4_lock_group(sb, i); list_for_each(cur, &grp->bb_prealloc_list) { pa = list_entry(cur, struct ext4_prealloc_space, @@ -5908,6 +5947,7 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode, struct buffer_head *bitmap_bh = NULL; struct super_block *sb = inode->i_sb; struct ext4_group_desc *gdp; + struct ext4_group_info *grp; unsigned int overflow; ext4_grpblk_t bit; struct buffer_head *gd_bh; @@ -5933,8 +5973,8 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode, overflow = 0; ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
- if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT( - ext4_get_group_info(sb, block_group)))) + grp = ext4_get_group_info(sb, block_group); + if (unlikely(!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp))) return;
/* @@ -6537,6 +6577,8 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
for (group = first_group; group <= last_group; group++) { grp = ext4_get_group_info(sb, group); + if (!grp) + continue; /* We only do this if the grp has never been initialized */ if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) { ret = ext4_mb_init_group(sb, group, GFP_NOFS); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index c527ec2b041fb..bf8a780cd69b6 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1017,6 +1017,8 @@ void ext4_mark_group_bitmap_corrupted(struct super_block *sb, struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL); int ret;
+ if (!grp || !gdp) + return; if (flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) { ret = ext4_test_and_set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT, &grp->bb_state);