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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html