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btrfs: harden parsing of compression mount options

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Btrfs happily but incorrectly accepts the `-o compress=zlib+foo` and similar
options with any random suffix.

Fix that by explicitly checking the end of the strings.

Signed-off-by: Daniel Vacek <neelx@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Daniel Vacek 2025-06-02 17:53:19 +02:00 committed by David Sterba
parent 3f0e865ae6
commit 3f093ccb95
1 changed files with 18 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

25
fs/btrfs/super.c
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@ -267,9 +267,19 @@ static inline blk_mode_t btrfs_open_mode(struct fs_context *fc)
return sb_open_mode(fc->sb_flags) & ~BLK_OPEN_RESTRICT_WRITES;
}
static bool btrfs_match_compress_type(const char *string, const char *type, bool may_have_level)
{
const int len = strlen(type);
return (strncmp(string, type, len) == 0) &&
((may_have_level && string[len] == ':') || string[len] == '\0');
}
static int btrfs_parse_compress(struct btrfs_fs_context *ctx,
const struct fs_parameter *param, int opt)
{
const char *string = param->string;
/*
* Provide the same semantics as older kernels that don't use fs
* context, specifying the "compress" option clears "force-compress"
@ -285,33 +295,34 @@ static int btrfs_parse_compress(struct btrfs_fs_context *ctx,
btrfs_set_opt(ctx->mount_opt, COMPRESS);
btrfs_clear_opt(ctx->mount_opt, NODATACOW);
btrfs_clear_opt(ctx->mount_opt, NODATASUM);
} else if (strncmp(param->string, "zlib", 4) == 0) {
} else if (btrfs_match_compress_type(string, "zlib", true)) {
ctx->compress_type = BTRFS_COMPRESS_ZLIB;
ctx->compress_level = btrfs_compress_str2level(BTRFS_COMPRESS_ZLIB,
param->string + 4);
string + 4);
btrfs_set_opt(ctx->mount_opt, COMPRESS);
btrfs_clear_opt(ctx->mount_opt, NODATACOW);
btrfs_clear_opt(ctx->mount_opt, NODATASUM);
} else if (strncmp(param->string, "lzo", 3) == 0) {
} else if (btrfs_match_compress_type(string, "lzo", false)) {
ctx->compress_type = BTRFS_COMPRESS_LZO;
ctx->compress_level = 0;
btrfs_set_opt(ctx->mount_opt, COMPRESS);
btrfs_clear_opt(ctx->mount_opt, NODATACOW);
btrfs_clear_opt(ctx->mount_opt, NODATASUM);
} else if (strncmp(param->string, "zstd", 4) == 0) {
} else if (btrfs_match_compress_type(string, "zstd", true)) {
ctx->compress_type = BTRFS_COMPRESS_ZSTD;
ctx->compress_level = btrfs_compress_str2level(BTRFS_COMPRESS_ZSTD,
param->string + 4);
string + 4);
btrfs_set_opt(ctx->mount_opt, COMPRESS);
btrfs_clear_opt(ctx->mount_opt, NODATACOW);
btrfs_clear_opt(ctx->mount_opt, NODATASUM);
} else if (strncmp(param->string, "no", 2) == 0) {
} else if (btrfs_match_compress_type(string, "no", false) ||
btrfs_match_compress_type(string, "none", false)) {
ctx->compress_level = 0;
ctx->compress_type = 0;
btrfs_clear_opt(ctx->mount_opt, COMPRESS);
btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
} else {
btrfs_err(NULL, "unrecognized compression value %s", param->string);
btrfs_err(NULL, "unrecognized compression value %s", string);
return -EINVAL;
}
return 0;