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module: Use RCU in find_symbol().

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module_assert_mutex_or_preempt() is not needed in find_symbol(). The
function checks for RCU-sched or the module_mutex to be acquired. The
list_for_each_entry_rcu() below does the same check.

Remove module_assert_mutex_or_preempt() from try_add_tainted_module().
Use RCU protection to invoke find_symbol() and update callers.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250108090457.512198-11-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
This commit is contained in:
Sebastian Andrzej Siewior
2025-01-08 10:04:39 +01:00
committed by Petr Pavlu
parent 435bbcc3be
commit 2ff49f8931
2 changed files with 19 additions and 25 deletions
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30
kernel/module/main.c
View File

@@ -331,7 +331,7 @@ static bool find_exported_symbol_in_section(const struct symsearch *syms,
/*
* Find an exported symbol and return it, along with, (optional) crc and
* (optional) module which owns it. Needs preempt disabled or module_mutex.
* (optional) module which owns it. Needs RCU or module_mutex.
*/
bool find_symbol(struct find_symbol_arg *fsa)
{
@@ -345,8 +345,6 @@ bool find_symbol(struct find_symbol_arg *fsa)
struct module *mod;
unsigned int i;
module_assert_mutex_or_preempt();
for (i = 0; i < ARRAY_SIZE(arr); i++)
if (find_exported_symbol_in_section(&arr[i], NULL, fsa))
return true;
@@ -812,10 +810,9 @@ void __symbol_put(const char *symbol)
.gplok = true,
};
preempt_disable();
guard(rcu)();
BUG_ON(!find_symbol(&fsa));
module_put(fsa.owner);
preempt_enable();
}
EXPORT_SYMBOL(__symbol_put);
@@ -1369,21 +1366,18 @@ void *__symbol_get(const char *symbol)
.warn = true,
};
preempt_disable();
if (!find_symbol(&fsa))
goto fail;
if (fsa.license != GPL_ONLY) {
pr_warn("failing symbol_get of non-GPLONLY symbol %s.\n",
symbol);
goto fail;
scoped_guard(rcu) {
if (!find_symbol(&fsa))
return NULL;
if (fsa.license != GPL_ONLY) {
pr_warn("failing symbol_get of non-GPLONLY symbol %s.\n",
symbol);
return NULL;
}
if (strong_try_module_get(fsa.owner))
return NULL;
}
if (strong_try_module_get(fsa.owner))
goto fail;
preempt_enable();
return (void *)kernel_symbol_value(fsa.sym);
fail:
preempt_enable();
return NULL;
}
EXPORT_SYMBOL_GPL(__symbol_get);

14
kernel/module/version.c
View File

@@ -79,17 +79,17 @@ int check_modstruct_version(const struct load_info *info,
.name = "module_layout",
.gplok = true,
};
bool have_symbol;
/*
* Since this should be found in kernel (which can't be removed), no
* locking is necessary -- use preempt_disable() to placate lockdep.
* locking is necessary. Regardless use a RCU read section to keep
* lockdep happy.
*/
preempt_disable();
if (!find_symbol(&fsa)) {
preempt_enable();
BUG();
}
preempt_enable();
scoped_guard(rcu)
have_symbol = find_symbol(&fsa);
BUG_ON(!have_symbol);
return check_version(info, "module_layout", mod, fsa.crc);
}