From: Michael Holzheu Date: Fri, 11 Sep 2009 08:28:59 +0000 (+0200) Subject: [S390] s390dbf: Add description for usage of "%s" in sprintf events X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=f64d04c042193183c6dad98944ae2861b998e8b7;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git [S390] s390dbf: Add description for usage of "%s" in sprintf events Using "%s" in sprintf event functions is dangerous. This patch adds a short description for this issue to the s390 debug feature documentation. Signed-off-by: Michael Holzheu Signed-off-by: Martin Schwidefsky --- diff --git a/Documentation/s390/s390dbf.txt b/Documentation/s390/s390dbf.txt index 2d10053dd97e..ae66f9b90a25 100644 --- a/Documentation/s390/s390dbf.txt +++ b/Documentation/s390/s390dbf.txt @@ -495,6 +495,13 @@ and for each vararg a long value. So e.g. for a debug entry with a format string plus two varargs one would need to allocate a (3 * sizeof(long)) byte data area in the debug_register() function. +IMPORTANT: Using "%s" in sprintf event functions is dangerous. You can only +use "%s" in the sprintf event functions, if the memory for the passed string is +available as long as the debug feature exists. The reason behind this is that +due to performance considerations only a pointer to the string is stored in +the debug feature. If you log a string that is freed afterwards, you will get +an OOPS when inspecting the debug feature, because then the debug feature will +access the already freed memory. NOTE: If using the sprintf view do NOT use other event/exception functions than the sprintf-event and -exception functions. diff --git a/arch/s390/include/asm/debug.h b/arch/s390/include/asm/debug.h index 31ed5686a968..18124b75a7ab 100644 --- a/arch/s390/include/asm/debug.h +++ b/arch/s390/include/asm/debug.h @@ -167,6 +167,10 @@ debug_text_event(debug_info_t* id, int level, const char* txt) return debug_event_common(id,level,txt,strlen(txt)); } +/* + * IMPORTANT: Use "%s" in sprintf format strings with care! Only pointers are + * stored in the s390dbf. See Documentation/s390/s390dbf.txt for more details! + */ extern debug_entry_t * debug_sprintf_event(debug_info_t* id,int level,char *string,...) __attribute__ ((format(printf, 3, 4))); @@ -206,7 +210,10 @@ debug_text_exception(debug_info_t* id, int level, const char* txt) return debug_exception_common(id,level,txt,strlen(txt)); } - +/* + * IMPORTANT: Use "%s" in sprintf format strings with care! Only pointers are + * stored in the s390dbf. See Documentation/s390/s390dbf.txt for more details! + */ extern debug_entry_t * debug_sprintf_exception(debug_info_t* id,int level,char *string,...) __attribute__ ((format(printf, 3, 4)));