From: Ryusuke Konishi konishi.ryusuke@gmail.com
[ Upstream commit ebeccaaef67a4895d2496ab8d9c2fb8d89201211 ]
If field s_log_block_size of superblock data is corrupted and too large, init_nilfs() and load_nilfs() still can trigger a shift-out-of-bounds warning followed by a kernel panic (if panic_on_warn is set):
shift exponent 38973 is too large for 32-bit type 'int' Call Trace: <TASK> dump_stack_lvl+0xcd/0x134 ubsan_epilogue+0xb/0x50 __ubsan_handle_shift_out_of_bounds.cold.12+0x17b/0x1f5 init_nilfs.cold.11+0x18/0x1d [nilfs2] nilfs_mount+0x9b5/0x12b0 [nilfs2] ...
This fixes the issue by adding and using a new helper function for getting block size with sanity check.
Link: https://lkml.kernel.org/r/20221027044306.42774-3-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Tested-by: Ryusuke Konishi konishi.ryusuke@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nilfs2/the_nilfs.c | 42 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c index 6a86acd35696..6aa6cef0757f 100644 --- a/fs/nilfs2/the_nilfs.c +++ b/fs/nilfs2/the_nilfs.c @@ -193,6 +193,34 @@ static int nilfs_store_log_cursor(struct the_nilfs *nilfs, return ret; }
+/** + * nilfs_get_blocksize - get block size from raw superblock data + * @sb: super block instance + * @sbp: superblock raw data buffer + * @blocksize: place to store block size + * + * nilfs_get_blocksize() calculates the block size from the block size + * exponent information written in @sbp and stores it in @blocksize, + * or aborts with an error message if it's too large. + * + * Return Value: On success, 0 is returned. If the block size is too + * large, -EINVAL is returned. + */ +static int nilfs_get_blocksize(struct super_block *sb, + struct nilfs_super_block *sbp, int *blocksize) +{ + unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size); + + if (unlikely(shift_bits > + ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)) { + nilfs_err(sb, "too large filesystem blocksize: 2 ^ %u KiB", + shift_bits); + return -EINVAL; + } + *blocksize = BLOCK_SIZE << shift_bits; + return 0; +} + /** * load_nilfs - load and recover the nilfs * @nilfs: the_nilfs structure to be released @@ -246,11 +274,15 @@ int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb) nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
/* verify consistency between two super blocks */ - blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size); + err = nilfs_get_blocksize(sb, sbp[0], &blocksize); + if (err) + goto scan_error; + if (blocksize != nilfs->ns_blocksize) { nilfs_warn(sb, "blocksize differs between two super blocks (%d != %d)", blocksize, nilfs->ns_blocksize); + err = -EINVAL; goto scan_error; }
@@ -609,9 +641,11 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data) if (err) goto failed_sbh;
- blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size); - if (blocksize < NILFS_MIN_BLOCK_SIZE || - blocksize > NILFS_MAX_BLOCK_SIZE) { + err = nilfs_get_blocksize(sb, sbp, &blocksize); + if (err) + goto failed_sbh; + + if (blocksize < NILFS_MIN_BLOCK_SIZE) { nilfs_err(sb, "couldn't mount because of unsupported filesystem blocksize %d", blocksize);