# \[PATCH\] powerpc/code-patching: Relax verification of patchability - Subsystems: LINUX FOR POWERPC (32-BIT AND 64-BIT), THE REST - Maintainers: Madhavan Srinivasan, Linus Torvalds - List: linuxppc-dev - 3 messages, 2 authors - Page: https://ratatoskr.run/linuxppc-dev/2021/11/1587364/t ## \[PATCH\] powerpc/code-patching: Relax verification of patchability - From: Christophe Leroy \ - Date: 2021-11-26 07:41:50 - Message: https://ratatoskr.run/linuxppc-dev/2021/11/1587364.md ```text 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 Reported-by: Stephen Rothwell Cc: Nicholas Piggin Fixes: 8b8a8f0ab3f5 ("powerpc/code-patching: Improve verification of patchability") Signed-off-by: Christophe Leroy --- 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)); + return do_patch_instruction(addr, instr); } NOKPROBE_SYMBOL(patch_instruction); -- 2.33.1 ``` ## Re: \[PATCH\] powerpc/code-patching: Relax verification of patchability - From: Christophe Leroy \ - Date: 2021-11-26 08:51:09 - Message: https://ratatoskr.run/linuxppc-dev/2021/11/1587436.md ```text Le 26/11/2021 à 08:39, Christophe Leroy a écrit : > 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 > Reported-by: Stephen Rothwell > Cc: Nicholas Piggin > Fixes: 8b8a8f0ab3f5 ("powerpc/code-patching: Improve verification of patchability") > Signed-off-by: Christophe Leroy > --- > 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); > ``` ## Re: \[PATCH\] powerpc/code-patching: Relax verification of patchability - From: Sachin Sant \ - Date: 2021-11-26 18:02:51 - Message: https://ratatoskr.run/linuxppc-dev/2021/11/1588047.md ```text > Running code patching self-tests ... > patch_instruction() called on invalid text address 0xe1011e58 from test_code_patching+0x34/0xd6c > > Reported-by: Sachin Sant > Reported-by: Stephen Rothwell > Cc: Nicholas Piggin > Fixes: 8b8a8f0ab3f5 ("powerpc/code-patching: Improve verification of patchability") > Signed-off-by: Christophe Leroy > --- > arch/powerpc/lib/code-patching.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > This fixes the problem for me. Tested-by: Sachin Sant Thanks -Sachin ```