mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-04-29 16:25:42 -04:00
3d8bba9535
In current xyarray code, xyarray__max_x() returns max_y, and xyarray__max_y()
returns max_x.
It's confusing and for code logic it looks not correct.
Error happens when closing evsel fd. Let's see this scenario:
1. Allocate an fd (pseudo-code)
perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
{
evsel->fd = xyarray__new(ncpus, nthreads, sizeof(int));
}
xyarray__new(int xlen, int ylen, size_t entry_size)
{
size_t row_size = ylen * entry_size;
struct xyarray *xy = zalloc(sizeof(*xy) + xlen * row_size);
xy->entry_size = entry_size;
xy->row_size = row_size;
xy->entries = xlen * ylen;
xy->max_x = xlen;
xy->max_y = ylen;
......
}
So max_x is ncpus, max_y is nthreads and row_size = nthreads * 4.
2. Use perf syscall and get the fd
int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
struct thread_map *threads)
{
for (cpu = 0; cpu < cpus->nr; cpu++) {
for (thread = 0; thread < nthreads; thread++) {
int fd, group_fd;
fd = sys_perf_event_open(&evsel->attr, pid, cpus->map[cpu],
group_fd, flags);
FD(evsel, cpu, thread) = fd;
}
}
static inline void *xyarray__entry(struct xyarray *xy, int x, int y)
{
return &xy->contents[x * xy->row_size + y * xy->entry_size];
}
These codes don't have issues. The issue happens in the closing of fd.
3. Close fd.
void perf_evsel__close_fd(struct perf_evsel *evsel)
{
int cpu, thread;
for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++)
for (thread = 0; thread < xyarray__max_y(evsel->fd); ++thread) {
close(FD(evsel, cpu, thread));
FD(evsel, cpu, thread) = -1;
}
}
Since xyarray__max_x() returns max_y (nthreads) and xyarry__max_y()
returns max_x (ncpus), so above code is actually to be:
for (cpu = 0; cpu < nthreads; cpu++)
for (thread = 0; thread < ncpus; ++thread) {
close(FD(evsel, cpu, thread));
FD(evsel, cpu, thread) = -1;
}
It's not correct!
This change is introduced by "475fb533fb7d" ("perf evsel: Fix buffer overflow
while freeing events")
This fix is to let xyarray__max_x() return max_x (ncpus) and
let xyarry__max_y() return max_y (nthreads)
Committer note:
This was also fixed by Ravi Bangoria, who provided the same patch,
noticing the problem with 'perf record':
<quote Ravi>
I see 'perf record -p <pid>' crashes with following log:
*** Error in `./perf': free(): invalid next size (normal): 0x000000000298b340 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7f7fd85c87e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7f7fd85d137a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f7fd85d553c]
./perf(perf_evsel__close+0xb4)[0x4b7614]
./perf(perf_evlist__delete+0x100)[0x4ab180]
./perf(cmd_record+0x1d9)[0x43a5a9]
./perf[0x49aa2f]
./perf(main+0x631)[0x427841]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7f7fd8571830]
./perf(_start+0x29)[0x427a59]
</>
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Fixes: d74be47673 ("perf xyarray: Save max_x, max_y")
Link: http://lkml.kernel.org/r/1508339478-26674-1-git-send-email-yao.jin@linux.intel.com
Link: http://lkml.kernel.org/r/1508327446-15302-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.