The crypto/zstd module has a double-free bug that occurs when multiple tfms are allocated and freed.

The issue happens because zstd_streams (per-CPU contexts) are freed in zstd_exit() during every tfm destruction, rather than being managed at the module level. When multiple tfms exist, each tfm exit attempts to free the same shared per-CPU streams, resulting in a double-free.

This leads to a stack trace similar to:

BUG: Bad page state in process kworker/u16:1 pfn:106fd93 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106fd93 flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) page_type: 0xffffffff() raw: 0017ffffc0000000 dead000000000100 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: nonzero entire_mapcount Modules linked in: ... CPU: 3 UID: 0 PID: 2506 Comm: kworker/u16:1 Kdump: loaded Tainted: G B Hardware name: ... Workqueue: btrfs-delalloc btrfs_work_helper Call Trace: <TASK> dump_stack_lvl+0x5d/0x80 bad_page+0x71/0xd0 free_unref_page_prepare+0x24e/0x490 free_unref_page+0x60/0x170 crypto_acomp_free_streams+0x5d/0xc0 crypto_acomp_exit_tfm+0x23/0x50 crypto_destroy_tfm+0x60/0xc0 ...

Change the lifecycle management of zstd_streams to free the streams only once during module cleanup.

Fixes: f5ad93ffb541 ("crypto: zstd - convert to acomp") Cc: stable@vger.kernel.org Signed-off-by: Giovanni Cabiddu giovanni.cabiddu@intel.com Reviewed-by: Suman Kumar Chakraborty suman.kumar.chakraborty@intel.com --- crypto/zstd.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/crypto/zstd.c b/crypto/zstd.c index dc5b36141ff8..cbbd0413751a 100644 --- a/crypto/zstd.c +++ b/crypto/zstd.c @@ -75,11 +75,6 @@ static int zstd_init(struct crypto_acomp *acomp_tfm) return ret; }

-static void zstd_exit(struct crypto_acomp *acomp_tfm) -{ - crypto_acomp_free_streams(&zstd_streams); -} - static int zstd_compress_one(struct acomp_req *req, struct zstd_ctx *ctx, const void *src, void *dst, unsigned int *dlen) { @@ -297,7 +292,6 @@ static struct acomp_alg zstd_acomp = { .cra_module = THIS_MODULE, }, .init = zstd_init, - .exit = zstd_exit, .compress = zstd_compress, .decompress = zstd_decompress, }; @@ -310,6 +304,7 @@ static int __init zstd_mod_init(void) static void __exit zstd_mod_fini(void) { crypto_unregister_acomp(&zstd_acomp); + crypto_acomp_free_streams(&zstd_streams); }

module_init(zstd_mod_init);

base-commit: 8faa5c4b47998c5930314a3bb8ee53534cfdc1ce