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With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function pointer
prototype to make sure the call target is valid to help mitigate ROP
attacks. If they are not identical, there is a failure at run time, which
manifests as either a kernel panic or thread getting killed. A proposed
warning in clang aims to catch these at compile time, which reveals:
drivers/scsi/elx/libefc/efc_node.c:811:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
ctx->current_state = state;
^ ~~~~~
drivers/scsi/elx/libefc/efc_node.c:878:21: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
node->nodedb_state = state;
^ ~~~~~
drivers/scsi/elx/libefc/efc_node.c:905:6: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' from 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') [-Werror,-Wincompatible-function-pointer-types-strict]
pf = node->nodedb_state;
^ ~~~~~~~~~~~~~~~~~~
drivers/scsi/elx/libefc/efc_device.c:455:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
node->nodedb_state = __efc_d_init;
^ ~~~~~~~~~~~~
drivers/scsi/elx/libefc/efc_sm.c:41:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
ctx->current_state = state;
^ ~~~~~
The type of the second parameter in the prototypes of ->current_state() and
->nodedb_state() ('u32') does not match the implementations, which have a
second parameter type of 'enum efc_sm_event'. Update the prototypes to have
the correct second parameter type, clearing up all the warnings and CFI
failures.
Link: https://github.com/ClangBuiltLinux/linux/issues/1750
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20221102161906.2781508-1-nathan@kernel.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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