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rds_info_getsockopt() reads a callback from rds_info_funcs and invokes it without protecting the callback's lifetime. Transport modules register functions stored in this array. For example, rds_tcp. ko registers rds_tcp_tc_info() for RDS_INFO_TCP_SOCKETS. </div>
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</head><body><pre style="font-family: sans-serif; font-size: 100%; white-space: pre-wrap; word-wrap: break-word">rds_info_getsockopt() reads a callback from rds_info_funcs and invokes it
without protecting the callback's lifetime. Transport modules register
functions stored in this array. For example, rds_tcp.ko registers
rds_tcp_tc_info() for RDS_INFO_TCP_SOCKETS.
This permits the following interleaving:
CPU0 CPU1
rds_info_getsockopt()
func = rds_tcp_tc_info
rmmod rds_tcp
rds_tcp_exit()
rds_info_deregister_func()
rds_info_funcs[offset] = NULL
free rds_tcp module text
func()
The reader can therefore branch to an address in unloaded module text.
Protect callback invocation with SRCU. Enter the SRCU read-side critical
section before loading the callback and leave it only after the callback
returns. Clear the callback with release semantics and call
synchronize_srcu() before deregistration returns, preventing module unload
from freeing its text while an old reader is still executing it. SRCU is
required because callbacks such as RDS_INFO_COUNTERS can sleep.
Keep the callback array unannotated and use acquire and release operations
for publication so sparse does not have to apply __rcu through the
function-pointer typedef. Replace the two callback-slot BUG_ON() checks
with WARN_ON_ONCE() and return without changing the slot on mismatch.
Link: https://lore.kernel.org/netdev/20260720184955.3008978-1-nicoyip.dev@gmail.com/
Suggested-by: Allison Henderson <achender@kernel.org>
Reviewed-by: Allison Henderson <achender@kernel.org>
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
---
Changes in v3:
- Use ordinary loads for callback-slot validation under rds_info_lock;
retain acquire semantics only for the lockless reader.
- Drop the Fixes tag because this patch targets net-next.
- Add Allison Henderson's Reviewed-by tag.
Link: https://lore.kernel.org/netdev/20260727174826.135662-1-nicoyip.dev@gmail.com/ [v2]
Changes in v2:
- Split the info callback/module-unload race from the independent
inc->i_conn lifetime bug.
- Keep the callback array unannotated and use smp_load_acquire() and
smp_store_release() to resolve the sparse errors.
- Replace the two touched callback-slot BUG_ON() checks with
WARN_ON_ONCE() error paths.
- Rewrite the commit message for the callback race and omit the unrelated
inc->i_conn KASAN report.
Link: https://lore.kernel.org/netdev/20260720184955.3008978-1-nicoyip.dev@gmail.com/ [v1]
net/rds/info.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/net/rds/info.c b/net/rds/info.c
index 21b32eb16559..385fefbfa07f 100644
--- a/net/rds/info.c
+++ b/net/rds/info.c
@@ -32,6 +32,7 @@
*/
#include <linux/percpu.h>
#include <linux/seq_file.h>
+#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/export.h>
@@ -68,6 +69,7 @@ struct rds_info_iterator {
unsigned long offset;
};
+DEFINE_STATIC_SRCU(rds_info_srcu);
static DEFINE_SPINLOCK(rds_info_lock);
static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
@@ -78,8 +80,12 @@ void rds_info_register_func(int optname, rds_info_func func)
BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
spin_lock(&rds_info_lock);
- BUG_ON(rds_info_funcs[offset]);
- rds_info_funcs[offset] = func;
+ if (WARN_ON_ONCE(rds_info_funcs[offset])) {
+ spin_unlock(&rds_info_lock);
+ return;
+ }
+ /* Pair with lockless callback lookup. */
+ smp_store_release(&rds_info_funcs[offset], func);
spin_unlock(&rds_info_lock);
}
EXPORT_SYMBOL_GPL(rds_info_register_func);
@@ -91,9 +97,14 @@ void rds_info_deregister_func(int optname, rds_info_func func)
BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
spin_lock(&rds_info_lock);
- BUG_ON(rds_info_funcs[offset] != func);
- rds_info_funcs[offset] = NULL;
+ if (WARN_ON_ONCE(rds_info_funcs[offset] != func)) {
+ spin_unlock(&rds_info_lock);
+ return;
+ }
+ /* Hide the callback before waiting for old readers. */
+ smp_store_release(&rds_info_funcs[offset], NULL);
spin_unlock(&rds_info_lock);
+ synchronize_srcu(&rds_info_srcu);
}
EXPORT_SYMBOL_GPL(rds_info_deregister_func);
@@ -165,6 +176,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt)
int npages = 0;
int ret;
int len;
+ int srcu_idx;
int total;
len = opt->optlen;
@@ -214,8 +226,11 @@ int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt)
rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
call_func:
- func = rds_info_funcs[optname - RDS_INFO_FIRST];
+ srcu_idx = srcu_read_lock(&rds_info_srcu);
+ /* Pair with callback slot publication and removal. */
+ func = smp_load_acquire(&rds_info_funcs[optname - RDS_INFO_FIRST]);
if (!func) {
+ srcu_read_unlock(&rds_info_srcu, srcu_idx);
ret = -ENOPROTOOPT;
goto out;
}
@@ -225,6 +240,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt)
iter.offset = offset0;
func(sock, len, &iter, &lens);
+ srcu_read_unlock(&rds_info_srcu, srcu_idx);
BUG_ON(lens.each == 0);
total = lens.nr * lens.each;
--
2.43.0
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