From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> Subject: squashfs: add option to panic on errors Add an errors=panic mount option to make squashfs trigger a panic when errors are encountered, similar to several other filesystems. This allows a kernel dump to be saved using which the corruption can be analysed and debugged. Inspired by a pre-fs_context patch by Anton Eliasson. Link: https://lkml.kernel.org/r/20210527125019.14511-1-vincent.whitchurch@xxxxxxxx Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> Signed-off-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/squashfs/block.c | 5 + fs/squashfs/squashfs_fs_sb.h | 1 fs/squashfs/super.c | 86 +++++++++++++++++++++++++++++++++ 3 files changed, 91 insertions(+), 1 deletion(-) --- a/fs/squashfs/block.c~squashfs-add-option-to-panic-on-errors +++ a/fs/squashfs/block.c @@ -226,8 +226,11 @@ out_free_bio: bio_free_pages(bio); bio_put(bio); out: - if (res < 0) + if (res < 0) { ERROR("Failed to read block 0x%llx: %d\n", index, res); + if (msblk->panic_on_errors) + panic("squashfs read failed"); + } return res; } --- a/fs/squashfs/squashfs_fs_sb.h~squashfs-add-option-to-panic-on-errors +++ a/fs/squashfs/squashfs_fs_sb.h @@ -65,5 +65,6 @@ struct squashfs_sb_info { unsigned int fragments; int xattr_ids; unsigned int ids; + bool panic_on_errors; }; #endif --- a/fs/squashfs/super.c~squashfs-add-option-to-panic-on-errors +++ a/fs/squashfs/super.c @@ -18,9 +18,11 @@ #include <linux/fs.h> #include <linux/fs_context.h> +#include <linux/fs_parser.h> #include <linux/vfs.h> #include <linux/slab.h> #include <linux/mutex.h> +#include <linux/seq_file.h> #include <linux/pagemap.h> #include <linux/init.h> #include <linux/module.h> @@ -37,6 +39,51 @@ static struct file_system_type squashfs_fs_type; static const struct super_operations squashfs_super_ops; +enum Opt_errors { + Opt_errors_continue, + Opt_errors_panic, +}; + +enum squashfs_param { + Opt_errors, +}; + +struct squashfs_mount_opts { + enum Opt_errors errors; +}; + +static const struct constant_table squashfs_param_errors[] = { + {"continue", Opt_errors_continue }, + {"panic", Opt_errors_panic }, + {} +}; + +static const struct fs_parameter_spec squashfs_fs_parameters[] = { + fsparam_enum("errors", Opt_errors, squashfs_param_errors), + {} +}; + +static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct squashfs_mount_opts *opts = fc->fs_private; + struct fs_parse_result result; + int opt; + + opt = fs_parse(fc, squashfs_fs_parameters, param, &result); + if (opt < 0) + return opt; + + switch (opt) { + case Opt_errors: + opts->errors = result.uint_32; + break; + default: + return -EINVAL; + } + + return 0; +} + static const struct squashfs_decompressor *supported_squashfs_filesystem( struct fs_context *fc, short major, short minor, short id) @@ -67,6 +114,7 @@ static const struct squashfs_decompresso static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc) { + struct squashfs_mount_opts *opts = fc->fs_private; struct squashfs_sb_info *msblk; struct squashfs_super_block *sblk = NULL; struct inode *root; @@ -85,6 +133,8 @@ static int squashfs_fill_super(struct su } msblk = sb->s_fs_info; + msblk->panic_on_errors = (opts->errors == Opt_errors_panic); + msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); @@ -350,18 +400,52 @@ static int squashfs_get_tree(struct fs_c static int squashfs_reconfigure(struct fs_context *fc) { + struct super_block *sb = fc->root->d_sb; + struct squashfs_sb_info *msblk = sb->s_fs_info; + struct squashfs_mount_opts *opts = fc->fs_private; + sync_filesystem(fc->root->d_sb); fc->sb_flags |= SB_RDONLY; + + msblk->panic_on_errors = (opts->errors == Opt_errors_panic); + return 0; } +static void squashfs_free_fs_context(struct fs_context *fc) +{ + kfree(fc->fs_private); +} + static const struct fs_context_operations squashfs_context_ops = { .get_tree = squashfs_get_tree, + .free = squashfs_free_fs_context, + .parse_param = squashfs_parse_param, .reconfigure = squashfs_reconfigure, }; +static int squashfs_show_options(struct seq_file *s, struct dentry *root) +{ + struct super_block *sb = root->d_sb; + struct squashfs_sb_info *msblk = sb->s_fs_info; + + if (msblk->panic_on_errors) + seq_puts(s, ",errors=panic"); + else + seq_puts(s, ",errors=continue"); + + return 0; +} + static int squashfs_init_fs_context(struct fs_context *fc) { + struct squashfs_mount_opts *opts; + + opts = kzalloc(sizeof(*opts), GFP_KERNEL); + if (!opts) + return -ENOMEM; + + fc->fs_private = opts; fc->ops = &squashfs_context_ops; return 0; } @@ -481,6 +565,7 @@ static struct file_system_type squashfs_ .owner = THIS_MODULE, .name = "squashfs", .init_fs_context = squashfs_init_fs_context, + .parameters = squashfs_fs_parameters, .kill_sb = kill_block_super, .fs_flags = FS_REQUIRES_DEV }; @@ -491,6 +576,7 @@ static const struct super_operations squ .free_inode = squashfs_free_inode, .statfs = squashfs_statfs, .put_super = squashfs_put_super, + .show_options = squashfs_show_options, }; module_init(init_squashfs_fs); _
