| Message ID | 20250411044456.1661380-1-zilin@seu.edu.cn (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [RFC] net/smc: Consider using kfree_sensitive() to free cpu_addr | expand |
On Fri, Apr 11, 2025 at 04:44:56AM +0000, Zilin Guan wrote: > Hello, > > In smcr_buf_unuse() and smc_buf_unuse(), memzero_explicit() is used to > clear cpu_addr when it is no longer in use, suggesting that cpu_addr > may contain sensitive information. > > To ensure proper handling of this sensitive memory, I propose using > kfree_sensitive()/kvfree_sensitive instead of kfree()/vfree() to free > cpu_addr in both smcd_buf_free() and smc_buf_free(). This change aims > to prevent potential sensitive data leaks. There is another possible meaning: memzero_explicit(conn->sndbuf_desc->cpu_addr, bufsize); WRITE_ONCE(conn->sndbuf_desc->used, 0); The WRITE_ONCE() probably tells the hardware the buffer is ready for it. In order to ensure they memzero has completed and that the compiler does not reorder the instructions you need a memory barrier: static inline void memzero_explicit(void *s, size_t count) { memset(s, 0, count); barrier_data(s); } So it could be using memzero_explicit() just for the barrier_data(). Please spend some time to analyze this code, look at the git history etc, see if there are any clues as to why memzero_explicit is used, or if there is any indication of sensitive information. Andrew
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index ac07b963aede..1b5eb0149b89 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1388,7 +1388,7 @@ static void smcr_buf_free(struct smc_link_group *lgr, bool is_rmb, if (!buf_desc->is_vm && buf_desc->pages) __free_pages(buf_desc->pages, buf_desc->order); else if (buf_desc->is_vm && buf_desc->cpu_addr) - vfree(buf_desc->cpu_addr); + kvfree_sensitive(buf_desc->cpu_addr, buf_desc->len); kfree(buf_desc); } @@ -1400,7 +1400,7 @@ static void smcd_buf_free(struct smc_link_group *lgr, bool is_dmb, buf_desc->len += sizeof(struct smcd_cdc_msg); smc_ism_unregister_dmb(lgr->smcd, buf_desc); } else { - kfree(buf_desc->cpu_addr); + kfree_sensitive(buf_desc->cpu_addr); } kfree(buf_desc); }
Hello, In smcr_buf_unuse() and smc_buf_unuse(), memzero_explicit() is used to clear cpu_addr when it is no longer in use, suggesting that cpu_addr may contain sensitive information. To ensure proper handling of this sensitive memory, I propose using kfree_sensitive()/kvfree_sensitive instead of kfree()/vfree() to free cpu_addr in both smcd_buf_free() and smc_buf_free(). This change aims to prevent potential sensitive data leaks. I am submitting this as an RFC to seek feedback on whether this change is appropriate and aligns with the subsystem's expectations. If confirmed to be useful, I will send a formal patch. Signed-off-by: Zilin Guan <zilin@seu.edu.cn> --- net/smc/smc_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)