From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx> Subject: rss_stat: add support to detect RSS updates of external mm When a process updates the RSS of a different process, the rss_stat tracepoint appears in the context of the process doing the update. This can confuse userspace that the RSS of process doing the update is updated, while in reality a different process's RSS was updated. This issue happens in reclaim paths such as with direct reclaim or background reclaim. This patch adds more information to the tracepoint about whether the mm being updated belongs to the current process's context (curr field). We also include a hash of the mm pointer so that the process who the mm belongs to can be uniquely identified (mm_id field). Also vsprintf.c is refactored a bit to allow reuse of hashing code. [akpm@xxxxxxxxxxxxxxxxxxxx: remove unused local `str'] [joelaf@xxxxxxxxxx: inline call to ptr_to_hashval] Link: http://lore.kernel.org/r/20191113153816.14b95acd@xxxxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20191114164622.GC233237@xxxxxxxxxx Link: http://lkml.kernel.org/r/20191106024452.81923-1-joel@xxxxxxxxxxxxxxxxx Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Reported-by: Ioannis Ilkos <ilkos@xxxxxxxxxx> Acked-by: Petr Mladek <pmladek@xxxxxxxx> [lib/vsprintf.c] Cc: Tim Murray <timmurray@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Carmen Jackson <carmenjackson@xxxxxxxxxx> Cc: Mayank Gupta <mayankgupta@xxxxxxxxxx> Cc: Daniel Colascione <dancol@xxxxxxxxxx> Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 8 +++--- include/linux/string.h | 2 + include/trace/events/kmem.h | 32 ++++++++++++++++++++++++--- lib/vsprintf.c | 40 ++++++++++++++++++++++++---------- mm/memory.c | 4 +-- 5 files changed, 66 insertions(+), 20 deletions(-) --- a/include/linux/mm.h~rss_stat-add-support-to-detect-rss-updates-of-external-mm +++ a/include/linux/mm.h @@ -1643,27 +1643,27 @@ static inline unsigned long get_mm_count return (unsigned long)val; } -void mm_trace_rss_stat(int member, long count); +void mm_trace_rss_stat(struct mm_struct *mm, int member, long count); static inline void add_mm_counter(struct mm_struct *mm, int member, long value) { long count = atomic_long_add_return(value, &mm->rss_stat.count[member]); - mm_trace_rss_stat(member, count); + mm_trace_rss_stat(mm, member, count); } static inline void inc_mm_counter(struct mm_struct *mm, int member) { long count = atomic_long_inc_return(&mm->rss_stat.count[member]); - mm_trace_rss_stat(member, count); + mm_trace_rss_stat(mm, member, count); } static inline void dec_mm_counter(struct mm_struct *mm, int member) { long count = atomic_long_dec_return(&mm->rss_stat.count[member]); - mm_trace_rss_stat(member, count); + mm_trace_rss_stat(mm, member, count); } /* Optimized variant when page is already known not to be PageAnon */ --- a/include/linux/string.h~rss_stat-add-support-to-detect-rss-updates-of-external-mm +++ a/include/linux/string.h @@ -216,6 +216,8 @@ int bprintf(u32 *bin_buf, size_t size, c extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos, const void *from, size_t available); +int ptr_to_hashval(const void *ptr, unsigned long *hashval_out); + /** * strstarts - does @str start with @prefix? * @str: string to examine --- a/include/trace/events/kmem.h~rss_stat-add-support-to-detect-rss-updates-of-external-mm +++ a/include/trace/events/kmem.h @@ -316,24 +316,50 @@ TRACE_EVENT(mm_page_alloc_extfrag, __entry->change_ownership) ); +/* + * Required for uniquely and securely identifying mm in rss_stat tracepoint. + */ +#ifndef __PTR_TO_HASHVAL +static unsigned int __maybe_unused mm_ptr_to_hash(const void *ptr) +{ + int ret; + unsigned long hashval; + + ret = ptr_to_hashval(ptr, &hashval); + if (ret) + return 0; + + /* The hashed value is only 32-bit */ + return (unsigned int)hashval; +} +#define __PTR_TO_HASHVAL +#endif + TRACE_EVENT(rss_stat, - TP_PROTO(int member, + TP_PROTO(struct mm_struct *mm, + int member, long count), - TP_ARGS(member, count), + TP_ARGS(mm, member, count), TP_STRUCT__entry( + __field(unsigned int, mm_id) + __field(unsigned int, curr) __field(int, member) __field(long, size) ), TP_fast_assign( + __entry->mm_id = mm_ptr_to_hash(mm); + __entry->curr = !!(current->mm == mm); __entry->member = member; __entry->size = (count << PAGE_SHIFT); ), - TP_printk("member=%d size=%ldB", + TP_printk("mm_id=%u curr=%d member=%d size=%ldB", + __entry->mm_id, + __entry->curr, __entry->member, __entry->size) ); --- a/lib/vsprintf.c~rss_stat-add-support-to-detect-rss-updates-of-external-mm +++ a/lib/vsprintf.c @@ -761,11 +761,38 @@ static int __init initialize_ptr_random( early_initcall(initialize_ptr_random); /* Maps a pointer to a 32 bit unique identifier. */ +static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out) +{ + unsigned long hashval; + + if (static_branch_unlikely(¬_filled_random_ptr_key)) + return -EAGAIN; + +#ifdef CONFIG_64BIT + hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key); + /* + * Mask off the first 32 bits, this makes explicit that we have + * modified the address (and 32 bits is plenty for a unique ID). + */ + hashval = hashval & 0xffffffff; +#else + hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key); +#endif + *hashval_out = hashval; + return 0; +} + +int ptr_to_hashval(const void *ptr, unsigned long *hashval_out) +{ + return __ptr_to_hashval(ptr, hashval_out); +} + static char *ptr_to_id(char *buf, char *end, const void *ptr, struct printf_spec spec) { const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)"; unsigned long hashval; + int ret; /* When debugging early boot use non-cryptographically secure hash. */ if (unlikely(debug_boot_weak_hash)) { @@ -773,22 +800,13 @@ static char *ptr_to_id(char *buf, char * return pointer_string(buf, end, (const void *)hashval, spec); } - if (static_branch_unlikely(¬_filled_random_ptr_key)) { + ret = __ptr_to_hashval(ptr, &hashval); + if (ret) { spec.field_width = 2 * sizeof(ptr); /* string length must be less than default_width */ return error_string(buf, end, str, spec); } -#ifdef CONFIG_64BIT - hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key); - /* - * Mask off the first 32 bits, this makes explicit that we have - * modified the address (and 32 bits is plenty for a unique ID). - */ - hashval = hashval & 0xffffffff; -#else - hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key); -#endif return pointer_string(buf, end, (const void *)hashval, spec); } --- a/mm/memory.c~rss_stat-add-support-to-detect-rss-updates-of-external-mm +++ a/mm/memory.c @@ -154,9 +154,9 @@ static int __init init_zero_pfn(void) } core_initcall(init_zero_pfn); -void mm_trace_rss_stat(int member, long count) +void mm_trace_rss_stat(struct mm_struct *mm, int member, long count) { - trace_rss_stat(member, count); + trace_rss_stat(mm, member, count); } #if defined(SPLIT_RSS_COUNTING) _
