Re: [Bug 216073] New: [s390x] kernel BUG at mm/usercopy.c:101! usercopy: Kernel memory exposure attempt detected from vmalloc 'n o area' (offset 0, size 1)!

[Matthew Wilcox <willy@infradead.org>]

On Sun, Jun 12, 2022 at 12:42:30PM +0800, Zorro Lang wrote:
> Looks likt it's not a s390x specific bug, I just hit this issue once (not 100%
> reproducible) on aarch64 with linux v5.19.0-rc1+ [1]. So back to cc linux-mm
> to get more review.
> 
> [1]
> [  980.200947] usercopy: Kernel memory exposure attempt detected from vmalloc 'no area' (offset 0, size 1)! 

       if (is_vmalloc_addr(ptr)) {
               struct vm_struct *area = find_vm_area(ptr);
               if (!area) {
                       usercopy_abort("vmalloc", "no area", to_user, 0, n);

Oh.  Looks like XFS uses vm_map_ram() and vm_map_ram() doesn't allocate
a vm_struct.

Ulad, how does this look to you?

diff --git a/mm/usercopy.c b/mm/usercopy.c
index baeacc735b83..6bc2a1407c59 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -173,7 +173,7 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 	}
 
 	if (is_vmalloc_addr(ptr)) {
-		struct vm_struct *area = find_vm_area(ptr);
+		struct vmap_area *area = find_vmap_area((unsigned long)ptr);
 		unsigned long offset;
 
 		if (!area) {
@@ -181,8 +181,9 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 			return;
 		}
 
-		offset = ptr - area->addr;
-		if (offset + n > get_vm_area_size(area))
+		/* XXX: We should also abort for free vmap_areas */
+		offset = (unsigned long)ptr - area->va_start;
+		if (offset + n >= area->va_end)
 			usercopy_abort("vmalloc", NULL, to_user, offset, n);
 		return;
 	}
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 07db42455dd4..effd1ff6a4b4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1798,7 +1798,7 @@ static void free_unmap_vmap_area(struct vmap_area *va)
 	free_vmap_area_noflush(va);
 }
 
-static struct vmap_area *find_vmap_area(unsigned long addr)
+struct vmap_area *find_vmap_area(unsigned long addr)
 {
 	struct vmap_area *va;
 

> [  980.200968] ------------[ cut here ]------------ 
> [  980.200969] kernel BUG at mm/usercopy.c:101! 
> [  980.201081] Internal error: Oops - BUG: 0 [#1] SMP 
> [  980.224192] Modules linked in: rfkill arm_spe_pmu mlx5_ib ast drm_vram_helper drm_ttm_helper ttm ib_uverbs acpi_ipmi drm_kms_helper ipmi_ssif fb_sys_fops syscopyarea sysfillrect ib_core sysimgblt arm_cmn arm_dmc620_pmu arm_dsu_pmu cppc_cpufreq sunrpc vfat fat drm fuse xfs libcrc32c mlx5_core crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce sbsa_gwdt nvme igb mlxfw nvme_core tls i2c_algo_bit psample pci_hyperv_intf i2c_designware_platform i2c_designware_core xgene_hwmon ipmi_devintf ipmi_msghandler 
> [  980.268449] CPU: 42 PID: 121940 Comm: rm Kdump: loaded Not tainted 5.19.0-rc1+ #1 
> [  980.275921] Hardware name: GIGABYTE R272-P30-JG/MP32-AR0-JG, BIOS F16f (SCP: 1.06.20210615) 07/01/2021 
> [  980.285214] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) 
> [  980.292165] pc : usercopy_abort+0x78/0x7c 
> [  980.296167] lr : usercopy_abort+0x78/0x7c 
> [  980.300166] sp : ffff80002b007730 
> [  980.303469] x29: ffff80002b007740 x28: ffff80002b007cc0 x27: ffffdc5683ecc880 
> [  980.310595] x26: 1ffff00005600f9b x25: ffffdc5681c90000 x24: ffff80002b007cdc 
> [  980.317722] x23: ffff800041a0004a x22: 0000000000000001 x21: 0000000000000001 
> [  980.324848] x20: 0000000000000000 x19: ffff800041a00049 x18: 0000000000000000 
> [  980.331974] x17: 2720636f6c6c616d x16: 76206d6f72662064 x15: 6574636574656420 
> [  980.339101] x14: 74706d6574746120 x13: 21293120657a6973 x12: ffff6106cbc4c03f 
> [  980.346227] x11: 1fffe106cbc4c03e x10: ffff6106cbc4c03e x9 : ffffdc5681f36e30 
> [  980.353353] x8 : ffff08365e2601f7 x7 : 0000000000000001 x6 : ffff6106cbc4c03e 
> [  980.360480] x5 : ffff08365e2601f0 x4 : 1fffe10044b11801 x3 : 0000000000000000 
> [  980.367606] x2 : 0000000000000000 x1 : ffff08022588c000 x0 : 000000000000005c 
> [  980.374733] Call trace: 
> [  980.377167]  usercopy_abort+0x78/0x7c 
> [  980.380819]  check_heap_object+0x3dc/0x3e0 
> [  980.384907]  __check_object_size.part.0+0x6c/0x1f0 
> [  980.389688]  __check_object_size+0x24/0x30 
> [  980.393774]  filldir64+0x548/0x84c 
> [  980.397165]  xfs_dir2_block_getdents+0x404/0x960 [xfs] 
> [  980.402437]  xfs_readdir+0x3c4/0x4b0 [xfs] 
> [  980.406652]  xfs_file_readdir+0x6c/0xa0 [xfs] 
> [  980.411127]  iterate_dir+0x3a4/0x500