This is a note to let you know that I've just added the patch titled
nilfs2: fix shift-out-of-bounds due to too large exponent of block size
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-fix-shift-out-of-bounds-due-to-too-large-expo.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f9e9e74a44b50035b7b7536572dd7481002f01c4
Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Date: Thu Oct 27 13:43:06 2022 +0900
nilfs2: fix shift-out-of-bounds due to too large exponent of block size
[ 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@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);
