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| author | Greg Thelen <gthelen@google.com> | 2021-11-10 18:18:14 -0800 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-11-11 13:09:34 +0100 |
| commit | 4716023a8f6a0f4a28047f14dd7ebdc319606b84 (patch) | |
| tree | b349726860336a253e7b136e72fc5da581a2fdc5 /kernel | |
| parent | 5863702561e625903ec678551cb056a4b19e0b8a (diff) | |
| download | lwn-4716023a8f6a0f4a28047f14dd7ebdc319606b84.tar.gz lwn-4716023a8f6a0f4a28047f14dd7ebdc319606b84.zip | |
perf/core: Avoid put_page() when GUP fails
PEBS PERF_SAMPLE_PHYS_ADDR events use perf_virt_to_phys() to convert PMU
sampled virtual addresses to physical using get_user_page_fast_only()
and page_to_phys().
Some get_user_page_fast_only() error cases return false, indicating no
page reference, but still initialize the output page pointer with an
unreferenced page. In these error cases perf_virt_to_phys() calls
put_page(). This causes page reference count underflow, which can lead
to unintentional page sharing.
Fix perf_virt_to_phys() to only put_page() if get_user_page_fast_only()
returns a referenced page.
Fixes: fc7ce9c74c3ad ("perf/core, x86: Add PERF_SAMPLE_PHYS_ADDR")
Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211111021814.757086-1-gthelen@google.com
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/core.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index f2253ea729a2..523106a506ee 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7154,7 +7154,6 @@ void perf_output_sample(struct perf_output_handle *handle, static u64 perf_virt_to_phys(u64 virt) { u64 phys_addr = 0; - struct page *p = NULL; if (!virt) return 0; @@ -7173,14 +7172,15 @@ static u64 perf_virt_to_phys(u64 virt) * If failed, leave phys_addr as 0. */ if (current->mm != NULL) { + struct page *p; + pagefault_disable(); - if (get_user_page_fast_only(virt, 0, &p)) + if (get_user_page_fast_only(virt, 0, &p)) { phys_addr = page_to_phys(p) + virt % PAGE_SIZE; + put_page(p); + } pagefault_enable(); } - - if (p) - put_page(p); } return phys_addr; |