On 21/12/2025 22.59, Sakari Ailus wrote: > Hi Daniel, > > Thanks for the patch. > > 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. > > This might not be the only case where -EEXIST may be returned by loading a > module.
That is correct. There are 40+ places detected and around 20+ more where the error is returned but at some point ignored and not propagated back to userspace. I have all the series ready for the first case, but I've only sent the first 6. > The patch is fine IMO but I'd just change -EEXIST to -EBUSY in e.g. > do_init_module() to avoid this being an actual bug elsewhere. We are planning to merge that too. Link [2] refers to Lucas's "[PATCH 0/2] module: Tweak return and warning" series, which replaces -EEXIST with -EBUSY at runtime and warns. However, we do not consider that to be the actual fix. I am starting to send these fixes out to avoid "spamming" unnecessarily the kernel log in cases we can already detect. > > I wonder what others think. Please, find the rest of the series sent: 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 FYI, these docs go on top of Lucas' changes with the hope this is clear in the docs. https://lore.kernel.org/all/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa7...@samsung.com > >> >> 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]
