Commit a914c6bc authored by Greg Thelen's avatar Greg Thelen Committed by Zheng Zengkai
Browse files

perf/core: Avoid put_page() when GUP fails 

stable inclusion
from stable-5.10.81
commit bd40513d0bee24095948abfaa17d3ad8f444a85b
bugzilla: 185832 https://gitee.com/openeuler/kernel/issues/I4L9CF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd40513d0bee24095948abfaa17d3ad8f444a85b



--------------------------------

commit 4716023a upstream.

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: fc7ce9c7 ("perf/core, x86: Add PERF_SAMPLE_PHYS_ADDR")
Signed-off-by: default avatarGreg Thelen <gthelen@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211111021814.757086-1-gthelen@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarChen Jun <chenjun102@huawei.com>
Acked-by: default avatarWeilong Chen <chenweilong@huawei.com>

Signed-off-by: default avatarChen Jun <chenjun102@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 624e847d

kernel/events/core.c

+5 −5
Original line number Diff line number Diff line
@@ -7036,7 +7036,6 @@ 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;
@@ -7055,14 +7054,15 @@ 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;