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static_call: Fix the module key fixup

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[ Upstream commit 50bf8080a94d171e843fc013abec19d8ab9f50ae ]

Provided the target address of a R_X86_64_PC32 relocation is aligned,
the low two bits should be invariant between the relative and absolute
value.

Turns out the address is not aligned and things go sideways, ensure we
transfer the bits in the absolute form when fixing up the key address.

Fixes: 73f44fe19d35 ("static_call: Allow module use without exposing static_call_key")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20210225220351.GE4746@worktop.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Peter Zijlstra 2021-02-25 23:03:51 +01:00 committed by Greg Kroah-Hartman
parent a63068e939
commit 0fefb5f3e5
1 changed files with 4 additions and 3 deletions
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7
kernel/static_call.c
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@ -358,7 +358,8 @@ static int static_call_add_module(struct module *mod)
struct static_call_site *site;
for (site = start; site != stop; site++) {
unsigned long addr = (unsigned long)static_call_key(site);
unsigned long s_key = (long)site->key + (long)&site->key;
unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;
unsigned long key;
/*
@ -382,8 +383,8 @@ static int static_call_add_module(struct module *mod)
return -EINVAL;
}
site->key = (key - (long)&site->key) |
(site->key & STATIC_CALL_SITE_FLAGS);
key |= s_key & STATIC_CALL_SITE_FLAGS;
site->key = key - (long)&site->key;
}
return __static_call_init(mod, start, stop);