[tip: x86/urgent] objtool: Fix pv_ops noinstr validation

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     988f01683c7f2bf9f8fe2bae1cf4010fcd1baaf5
Gitweb:        https://git.kernel.org/tip/988f01683c7f2bf9f8fe2bae1cf4010fcd1baaf5
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Thu, 02 Dec 2021 21:45:34 +01:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Fri, 03 Dec 2021 09:11:42 +01:00

objtool: Fix pv_ops noinstr validation

Boris reported that in one of his randconfig builds, objtool got
infinitely stuck. Turns out there's trivial list corruption in the
pv_ops tracking when a function is both in a static table and in a code
assignment.

Avoid re-adding function to the pv_ops[] lists when they're already on
it.

Fixes: db2b0c5d7b6f ("objtool: Support pv_opsindirect calls for noinstr")
Reported-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Tested-by: Borislav Petkov <bp@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20211202204534.GA16608@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
 tools/objtool/elf.c     | 1 +
 tools/objtool/objtool.c | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 81a4c54..4b384c9 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -375,6 +375,7 @@ static int read_symbols(struct elf *elf)
 			return -1;
 		}
 		memset(sym, 0, sizeof(*sym));
+		INIT_LIST_HEAD(&sym->pv_target);
 		sym->alias = sym;
 
 		sym->idx = i;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index c90c708..bdf699f 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -153,6 +153,10 @@ void objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
 	    !strcmp(func->name, "_paravirt_ident_64"))
 		return;
 
+	/* already added this function */
+	if (!list_empty(&func->pv_target))
+		return;
+
 	list_add(&func->pv_target, &f->pv_ops[idx].targets);
 	f->pv_ops[idx].clean = false;
 }