Re: [PATCH] powerpc/code-patching: Relax verification of patchability
From: Christophe Leroy <hidden>
Date: 2021-11-26 08:51:09
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Le 26/11/2021 à 08:39, Christophe Leroy a écrit :
quoted hunk ↗ jump to hunk
Commit 8b8a8f0ab3f5 ("powerpc/code-patching: Improve verification of patchability") introduced a stricter verification of the patched area by checking it is proper kernel text. But as least two usages of patch_instruction() fall outside: - Code patching selftests, which use stack and vmalloc space. - Ftrace So for the time being, partially revert commit 8b8a8f0ab3f5 and add a onetime warning: Running code patching self-tests ... patch_instruction() called on invalid text address 0xe1011e58 from test_code_patching+0x34/0xd6c Reported-by: Sachin Sant <redacted> Reported-by: Stephen Rothwell <redacted> Cc: Nicholas Piggin <npiggin@gmail.com> Fixes: 8b8a8f0ab3f5 ("powerpc/code-patching: Improve verification of patchability") Signed-off-by: Christophe Leroy <redacted> --- arch/powerpc/lib/code-patching.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 1dd636a85cc1..c87eea773930 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c@@ -190,9 +190,13 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr) int patch_instruction(u32 *addr, struct ppc_inst instr) { /* Make sure we aren't patching a freed init section */ - if (!kernel_text_address((unsigned long)addr)) + if (system_state >= SYSTEM_FREEING_INITMEM && init_section_contains(addr, 4)) return 0; + if (!kernel_text_address((unsigned long)addr)) + pr_warn_once("%s() called on invalid text address 0x%p from %pS\n", + __func__, addr, __builtin_return_address(0)); +
May it be better to use pr_warn_ratelimited() instead in order to catch more than the first occurence ?
return do_patch_instruction(addr, instr); } NOKPROBE_SYMBOL(patch_instruction);