[PATCH 1/2] perf tools: Check kptr_restrict for root

[PATCH 1/2] perf tools: Check kptr_restrict for root

[Wang Nan]

If kptr_restrict is set to 2, even root is not allowed to see pointers.
This patch checks kptr_restrict even if euid == 0. For root, report
error if kptr_restrict is 2.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/symbol.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 20f9cb3..54c4ff2 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1933,17 +1933,17 @@ int setup_intlist(struct intlist **list, const char *list_str,
 static bool symbol__read_kptr_restrict(void)
 {
 	bool value = false;
+	FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
 
-	if (geteuid() != 0) {
-		FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
-		if (fp != NULL) {
-			char line[8];
+	if (fp != NULL) {
+		char line[8];
 
-			if (fgets(line, sizeof(line), fp) != NULL)
-				value = atoi(line) != 0;
+		if (fgets(line, sizeof(line), fp) != NULL)
+			value = (geteuid() != 0) ?
+					(atoi(line) != 0) :
+					(atoi(line) == 2);
 
-			fclose(fp);
-		}
+		fclose(fp);
 	}
 
 	return value;
-- 
1.8.3.4

[PATCH 2/2] perf record: Fix crash when kptr is restricted

[Wang Nan]

Before this patch, a simple 'perf record' could fail if kptr_restrict
is set to 1 (for normal user) or 2 (for root):

 # perf record ls
 WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
 check /proc/sys/kernel/kptr_restrict.

 Samples in kernel functions may not be resolved if a suitable vmlinux
 file is not found in the buildid cache or in the vmlinux path.

 Samples in kernel modules won't be resolved at all.

 If some relocation was applied (e.g. kexec) symbols may be misresolved
 even with a suitable vmlinux or kallsyms file.

 Segmentation fault (core dumped)

This patch skips perf_event__synthesize_kernel_mmap() when kptr is not
available.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/event.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index f6fcc68..9b141f1 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -673,6 +673,8 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
 	int err;
 	union perf_event *event;
 
+	if (symbol_conf.kptr_restrict)
+		return -1;
 	if (map == NULL)
 		return -1;
 
-- 
1.8.3.4

Re: [PATCH 2/2] perf record: Fix crash when kptr is restricted

[Arnaldo Carvalho de Melo]

Em Tue, May 24, 2016 at 09:21:28AM +0000, Wang Nan escreveu:
> Before this patch, a simple 'perf record' could fail if kptr_restrict
> is set to 1 (for normal user) or 2 (for root):

sorry, hadn't seen this one, applying. :-)

- Arnaldo
 
>  # perf record ls
>  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
>  check /proc/sys/kernel/kptr_restrict.
> 
>  Samples in kernel functions may not be resolved if a suitable vmlinux
>  file is not found in the buildid cache or in the vmlinux path.
> 
>  Samples in kernel modules won't be resolved at all.
> 
>  If some relocation was applied (e.g. kexec) symbols may be misresolved
>  even with a suitable vmlinux or kallsyms file.
> 
>  Segmentation fault (core dumped)
> 
> This patch skips perf_event__synthesize_kernel_mmap() when kptr is not
> available.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  tools/perf/util/event.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index f6fcc68..9b141f1 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -673,6 +673,8 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
>  	int err;
>  	union perf_event *event;
>  
> +	if (symbol_conf.kptr_restrict)
> +		return -1;
>  	if (map == NULL)
>  		return -1;
>  
> -- 
> 1.8.3.4

Re: [PATCH 2/2] perf record: Fix crash when kptr is restricted

[Arnaldo Carvalho de Melo]

Em Tue, May 24, 2016 at 09:21:28AM +0000, Wang Nan escreveu:
> Before this patch, a simple 'perf record' could fail if kptr_restrict
> is set to 1 (for normal user) or 2 (for root):
> 
>  # perf record ls
>  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
>  check /proc/sys/kernel/kptr_restrict.
> 
>  Samples in kernel functions may not be resolved if a suitable vmlinux
>  file is not found in the buildid cache or in the vmlinux path.
> 
>  Samples in kernel modules won't be resolved at all.
> 
>  If some relocation was applied (e.g. kexec) symbols may be misresolved
>  even with a suitable vmlinux or kallsyms file.
> 
>  Segmentation fault (core dumped)
> 
> This patch skips perf_event__synthesize_kernel_mmap() when kptr is not
> available.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>

Thanks, applied and added a:

Fixes: 45e90056904b ("perf machine: Do not bail out if not managing to read ref reloc symbol")

But I'll investigate a bit more later, as the patch fixes the problem,
but I think probably it'd be better to check what is not being set up
in the ref reloc symbol stuff not bailed out by the patch above.

- Arnaldo

> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  tools/perf/util/event.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index f6fcc68..9b141f1 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -673,6 +673,8 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
>  	int err;
>  	union perf_event *event;
>  
> +	if (symbol_conf.kptr_restrict)
> +		return -1;
>  	if (map == NULL)
>  		return -1;
>  
> -- 
> 1.8.3.4

[tip:perf/urgent] perf record: Fix crash when kptr is restricted

[tip-bot for Wang Nan]

Commit-ID:  3dc6c1d54ff4cc9ce7e8513c286c970304cde20b
Gitweb:     http://git.kernel.org/tip/3dc6c1d54ff4cc9ce7e8513c286c970304cde20b
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Tue, 24 May 2016 09:21:28 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 27 May 2016 09:41:39 -0300

perf record: Fix crash when kptr is restricted

Before this patch, a simple 'perf record' could fail if kptr_restrict is
set to 1 (for normal user) or 2 (for root):

  # perf record ls
  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
  check /proc/sys/kernel/kptr_restrict.

  Samples in kernel functions may not be resolved if a suitable vmlinux
  file is not found in the buildid cache or in the vmlinux path.

  Samples in kernel modules won't be resolved at all.

  If some relocation was applied (e.g. kexec) symbols may be misresolved
  even with a suitable vmlinux or kallsyms file.

  Segmentation fault (core dumped)

This patch skips perf_event__synthesize_kernel_mmap() when kptr is not
available.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Fixes: 45e90056904b ("perf machine: Do not bail out if not managing to read ref reloc symbol")
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464081688-167940-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/event.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index f6fcc68..9b141f1 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -673,6 +673,8 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
 	int err;
 	union perf_event *event;
 
+	if (symbol_conf.kptr_restrict)
+		return -1;
 	if (map == NULL)
 		return -1;
 

Re: [PATCH 1/2] perf tools: Check kptr_restrict for root

[Arnaldo Carvalho de Melo]

Em Tue, May 24, 2016 at 09:21:27AM +0000, Wang Nan escreveu:
> If kptr_restrict is set to 2, even root is not allowed to see pointers.
> This patch checks kptr_restrict even if euid == 0. For root, report
> error if kptr_restrict is 2.

Improves the situation, but kptr_restrict=2 still causes a segfault:


[root@jouet ~]# echo 2 > /proc/sys/kernel/kptr_restrict 
[root@jouet ~]# perf record usleep 1
Segmentation fault (core dumped)
[root@jouet ~]# echo 1 > /proc/sys/kernel/kptr_restrict 
[root@jouet ~]# perf record usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (8 samples) ]
[root@jouet ~]# echo 2 > /proc/sys/kernel/kptr_restrict 
[root@jouet ~]# perf record usleep 1
WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
check /proc/sys/kernel/kptr_restrict.

Samples in kernel functions may not be resolved if a suitable vmlinux
file is not found in the buildid cache or in the vmlinux path.

Samples in kernel modules won't be resolved at all.

If some relocation was applied (e.g. kexec) symbols may be misresolved
even with a suitable vmlinux or kallsyms file.

Segmentation fault (core dumped)
[root@jouet ~]# 

Applying your patch and then investigating this other one.

Thanks,

- Arnaldo
 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  tools/perf/util/symbol.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 20f9cb3..54c4ff2 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1933,17 +1933,17 @@ int setup_intlist(struct intlist **list, const char *list_str,
>  static bool symbol__read_kptr_restrict(void)
>  {
>  	bool value = false;
> +	FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
>  
> -	if (geteuid() != 0) {
> -		FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
> -		if (fp != NULL) {
> -			char line[8];
> +	if (fp != NULL) {
> +		char line[8];
>  
> -			if (fgets(line, sizeof(line), fp) != NULL)
> -				value = atoi(line) != 0;
> +		if (fgets(line, sizeof(line), fp) != NULL)
> +			value = (geteuid() != 0) ?
> +					(atoi(line) != 0) :
> +					(atoi(line) == 2);
>  
> -			fclose(fp);
> -		}
> +		fclose(fp);
>  	}
>  
>  	return value;
> -- 
> 1.8.3.4

[tip:perf/urgent] perf symbols: Check kptr_restrict for root

[tip-bot for Wang Nan]

Commit-ID:  38272dc4f1b17437871b786d567e1242d0904f5a
Gitweb:     http://git.kernel.org/tip/38272dc4f1b17437871b786d567e1242d0904f5a
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Tue, 24 May 2016 09:21:27 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 27 May 2016 09:41:23 -0300

perf symbols: Check kptr_restrict for root

If kptr_restrict is set to 2, even root is not allowed to see pointers.
This patch checks kptr_restrict even if euid == 0. For root, report
error if kptr_restrict is 2.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464081688-167940-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/symbol.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 20f9cb3..54c4ff2 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1933,17 +1933,17 @@ int setup_intlist(struct intlist **list, const char *list_str,
 static bool symbol__read_kptr_restrict(void)
 {
 	bool value = false;
+	FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
 
-	if (geteuid() != 0) {
-		FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
-		if (fp != NULL) {
-			char line[8];
+	if (fp != NULL) {
+		char line[8];
 
-			if (fgets(line, sizeof(line), fp) != NULL)
-				value = atoi(line) != 0;
+		if (fgets(line, sizeof(line), fp) != NULL)
+			value = (geteuid() != 0) ?
+					(atoi(line) != 0) :
+					(atoi(line) == 2);
 
-			fclose(fp);
-		}
+		fclose(fp);
 	}
 
 	return value;