On 22/12/2025 09.19, Greg Kroah-Hartman wrote: > On Sat, Dec 20, 2025 at 04:55:00AM +0100, Daniel Gomez wrote: >> From: Daniel Gomez <[email protected]> >> >> The -EEXIST error code is reserved by the module loading infrastructure >> to indicate that a module is already loaded. When a module's init >> function returns -EEXIST, userspace tools like kmod interpret this as >> "module already loaded" and treat the operation as successful, returning >> 0 to the user even though the module initialization actually failed. >> >> This follows the precedent set by commit 54416fd76770 ("netfilter: >> conntrack: helper: Replace -EEXIST by -EBUSY") which fixed the same >> issue in nf_conntrack_helper_register(). >> >> Affected modules: >> * meraki_mx100 pcengines_apuv2 >> >> Signed-off-by: Daniel Gomez <[email protected]> >> --- >> The error code -EEXIST is reserved by the kernel module loader to >> indicate that a module with the same name is already loaded. When a >> module's init function returns -EEXIST, kmod interprets this as "module >> already loaded" and reports success instead of failure [1]. >> >> The kernel module loader will include a safety net that provides -EEXIST >> to -EBUSY with a warning [2], and a documentation patch has been sent to >> prevent future occurrences [3]. >> >> These affected code paths were identified using a static analysis tool >> [4] that traces -EEXIST returns to module_init(). The tool was developed >> with AI assistance and all findings were manually validated. >> >> Link: https://lore.kernel.org/all/[email protected]/ [1] >> Link: >> https://lore.kernel.org/all/[email protected]/ >> [2] >> Link: >> https://lore.kernel.org/all/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa7...@samsung.com/ >> [3] >> Link: https://gitlab.com/-/snippets/4913469 [4] >> --- >> drivers/base/swnode.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c >> index 16a8301c25d6..083593d99a18 100644 >> --- a/drivers/base/swnode.c >> +++ b/drivers/base/swnode.c >> @@ -919,7 +919,7 @@ int software_node_register(const struct software_node >> *node) >> struct swnode *parent = software_node_to_swnode(node->parent); >> >> if (software_node_to_swnode(node)) >> - return -EEXIST; >> + return -EBUSY; > > While I understand the want for the module loader to be returning > -EBUSY, that doesn't really make sense down here in this layer of the > kernel. > > So why doesn't the module loader turn -EEXIST return values into -EBUSY > if it wishes to pass that value on to userspace? Otherwise you are
Indeed, we are planning to do that as well with "[PATCH 0/2] module: Tweak return and warning": https://lore.kernel.org/all/[email protected]/#t However, we don't consider that as the right fix. > going to be constantly playing "whack-a-mole" here and have really > set things up so that NO api can ever return EEXIST as an error value in > the future. 100%. For that reason, on top of the series from Lucas, we are documenting this to make it clear: https://lore.kernel.org/linux-modules/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa7...@samsung.com/T/#m2ed6fbffb3f78b9bff53840f6492a198c389cb50 And sending patches where we see modules need fixing. I have already sent 6 out of 20-ish series (that include a total of 40+ fixes): https://lore.kernel.org/all/20251220-dev-module-init-eexists-linux-scsi-v1-0-5379db749...@samsung.com https://lore.kernel.org/all/20251219-dev-module-init-eexists-netfilter-v1-1-efd3f6241...@samsung.com https://lore.kernel.org/all/20251220-dev-module-init-eexists-bpf-v1-1-7f186663d...@samsung.com https://lore.kernel.org/all/20251220-dev-module-init-eexists-keyring-v1-1-a2f23248c...@samsung.com https://lore.kernel.org/all/20251220-dev-module-init-eexists-dm-devel-v1-1-90ed00444...@samsung.com
