Subject: + lib-vsprintf-add-%pt-format-specifier.patch added to -mm tree
To: penguin-kernel@xxxxxxxxxxxxxxxxxxx,keescook@xxxxxxxxxxxx,pavel@xxxxxx,penguin-kernel@xxxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 10 Jan 2014 16:01:02 -0800
The patch titled
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
has been added to the -mm tree. Its filename is
lib-vsprintf-add-%pt-format-specifier.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-vsprintf-add-%pt-format-specifier.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-vsprintf-add-%pt-format-specifier.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: lib/vsprintf: add %pT format specifier
Since task_struct->comm can be modified by other threads while the current
thread is reading it, it is recommended to use get_task_comm() for reading
it.
However, since get_task_comm() holds task_struct->alloc_lock spinlock,
some users cannot use get_task_comm(). Also, a lot of users are directly
reading from task_struct->comm even if they can use get_task_comm(). Such
users might obtain inconsistent result.
This patch introduces %pT format specifier for printing task_struct->comm.
Currently %pT does not provide consistency. I'm planning to change to
use RCU in the future. By using RCU, the comm name read from
task_struct->comm will be guaranteed to be consistent. But before
modifying set_task_comm() to use RCU, we need to kill direct ->comm users
who do not use get_task_comm().
An example for converting direct ->comm users is shown below. Since many
debug printings use p == current, you can pass NULL instead of p if p ==
current.
pr_info("comm=%s\n", p->comm); => pr_info("comm=%pT\n", p);
pr_info("comm=%s\n", current->comm); => pr_info("comm=%pT\n", NULL);
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Pavel Machek <pavel@xxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/printk-formats.txt | 6 ++++++
lib/vsprintf.c | 20 +++++++++++++++++++-
2 files changed, 25 insertions(+), 1 deletion(-)
diff -puN Documentation/printk-formats.txt~lib-vsprintf-add-%pt-format-specifier Documentation/printk-formats.txt
--- a/Documentation/printk-formats.txt~lib-vsprintf-add-%pt-format-specifier
+++ a/Documentation/printk-formats.txt
@@ -184,6 +184,12 @@ dentry names:
equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
n last components. %pD does the same thing for struct file.
+task_struct comm name:
+
+ %pT
+
+ For printing task_struct->comm.
+
struct va_format:
%pV
diff -puN lib/vsprintf.c~lib-vsprintf-add-%pt-format-specifier lib/vsprintf.c
--- a/lib/vsprintf.c~lib-vsprintf-add-%pt-format-specifier
+++ a/lib/vsprintf.c
@@ -1179,6 +1179,21 @@ char *address_val(char *buf, char *end,
return number(buf, end, num, spec);
}
+static noinline_for_stack
+char *comm_name(char *buf, char *end, struct task_struct *tsk,
+ struct printf_spec spec, const char *fmt)
+{
+ char name[TASK_COMM_LEN];
+
+ /* Caller can pass NULL instead of current. */
+ if (!tsk)
+ tsk = current;
+ /* Not using get_task_comm() in case I'm in IRQ context. */
+ memcpy(name, tsk->comm, TASK_COMM_LEN);
+ name[sizeof(name) - 1] = '\0';
+ return string(buf, end, name, spec);
+}
+
int kptr_restrict __read_mostly;
/*
@@ -1246,6 +1261,7 @@ int kptr_restrict __read_mostly;
* (default assumed to be phys_addr_t, passed by reference)
* - 'd[234]' For a dentry name (optionally 2-4 last components)
* - 'D[234]' Same as 'd' but for a struct file
+ * - 'T' task_struct->comm
*
* Note: The difference between 'S' and 'F' is that on ia64 and ppc64
* function pointers are really function descriptors, which contain a
@@ -1257,7 +1273,7 @@ char *pointer(const char *fmt, char *buf
{
int default_width = 2 * sizeof(void *) + (spec.flags & SPECIAL ? 2 : 0);
- if (!ptr && *fmt != 'K') {
+ if (!ptr && *fmt != 'K' && *fmt != 'T') {
/*
* Print (null) with the same width as a pointer so it makes
* tabular output look nice.
@@ -1385,6 +1401,8 @@ char *pointer(const char *fmt, char *buf
return dentry_name(buf, end,
((const struct file *)ptr)->f_path.dentry,
spec, fmt);
+ case 'T':
+ return comm_name(buf, end, ptr, spec, fmt);
}
spec.flags |= SMALL;
if (spec.field_width == -1) {
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
lib-vsprintf-add-%pt-format-specifier.patch
init-fix-possible-format-string-bug.patch
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