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Message-Id: <20220819094952.2602066-1-jens.wiklander@linaro.org>
Date: Fri, 19 Aug 2022 11:49:52 +0200
From: Jens Wiklander <jens.wiklander@...aro.org>
To: linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org
Cc: Sumit Garg <sumit.garg@...aro.org>,
Jerome Forissier <jerome.forissier@...aro.org>,
Jens Wiklander <jens.wiklander@...aro.org>,
stable@...r.kernel.org, Nimish Mishra <neelam.nimish@...il.com>,
Anirban Chakraborty <ch.anirban00727@...il.com>,
Debdeep Mukhopadhyay <debdeep.mukhopadhyay@...il.com>,
Linus Torvalds <torvalds@...uxfoundation.org>
Subject: [PATCH v3] tee: add overflow check in register_shm_helper()
With special lengths supplied by user space, register_shm_helper() has
an integer overflow when calculating the number of pages covered by a
supplied user space memory region. This causes
internal_get_user_pages_fast() a helper function of
pin_user_pages_fast() to do a NULL pointer dereference.
[ 14.141620] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
[ 14.142556] Mem abort info:
[ 14.142829] ESR = 0x0000000096000044
[ 14.143237] EC = 0x25: DABT (current EL), IL = 32 bits
[ 14.143742] SET = 0, FnV = 0
[ 14.144052] EA = 0, S1PTW = 0
[ 14.144348] FSC = 0x04: level 0 translation fault
[ 14.144767] Data abort info:
[ 14.145053] ISV = 0, ISS = 0x00000044
[ 14.145394] CM = 0, WnR = 1
[ 14.145766] user pgtable: 4k pages, 48-bit VAs, pgdp=000000004278e000
[ 14.146279] [0000000000000010] pgd=0000000000000000, p4d=0000000000000000
[ 14.147435] Internal error: Oops: 96000044 [#1] PREEMPT SMP
[ 14.148026] Modules linked in:
[ 14.148595] CPU: 1 PID: 173 Comm: optee_example_a Not tainted 5.19.0 #11
[ 14.149204] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
[ 14.149832] pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 14.150481] pc : internal_get_user_pages_fast+0x474/0xa80
[ 14.151640] lr : internal_get_user_pages_fast+0x404/0xa80
[ 14.152408] sp : ffff80000a88bb30
[ 14.152711] x29: ffff80000a88bb30 x28: 0000fffff836d000 x27: 0000fffff836e000
[ 14.153580] x26: fffffc0000000000 x25: fffffc0000f4a1c0 x24: ffff00000289fb70
[ 14.154634] x23: ffff000002702e08 x22: 0000000000040001 x21: ffff8000097eec60
[ 14.155378] x20: 0000000000f4a1c0 x19: 00e800007d287f43 x18: 0000000000000000
[ 14.156215] x17: 0000000000000000 x16: 0000000000000000 x15: 0000fffff836cfb0
[ 14.157068] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
[ 14.157747] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
[ 14.158576] x8 : ffff00000276ec80 x7 : 0000000000000000 x6 : 000000000000003f
[ 14.159243] x5 : 0000000000000000 x4 : ffff000041ec4eac x3 : ffff000002774cb8
[ 14.159977] x2 : 0000000000000004 x1 : 0000000000000010 x0 : 0000000000000000
[ 14.160883] Call trace:
[ 14.161166] internal_get_user_pages_fast+0x474/0xa80
[ 14.161763] pin_user_pages_fast+0x24/0x4c
[ 14.162227] register_shm_helper+0x194/0x330
[ 14.162734] tee_shm_register_user_buf+0x78/0x120
[ 14.163290] tee_ioctl+0xd0/0x11a0
[ 14.163739] __arm64_sys_ioctl+0xa8/0xec
[ 14.164227] invoke_syscall+0x48/0x114
[ 14.164653] el0_svc_common.constprop.0+0x44/0xec
[ 14.165130] do_el0_svc+0x2c/0xc0
[ 14.165498] el0_svc+0x2c/0x84
[ 14.165847] el0t_64_sync_handler+0x1ac/0x1b0
[ 14.166258] el0t_64_sync+0x18c/0x190
[ 14.166878] Code: 91002318 11000401 b900f7e1 f9403be1 (f820d839)
[ 14.167666] ---[ end trace 0000000000000000 ]---
Fix this by adding an overflow check when calculating the end of the
memory range. Also add an explicit call to access_ok() in
tee_shm_register_user_buf() to catch an invalid user space address
early.
Fixes: 033ddf12bcf5 ("tee: add register user memory")
Cc: stable@...r.kernel.org
Reported-by: Nimish Mishra <neelam.nimish@...il.com>
Reported-by: Anirban Chakraborty <ch.anirban00727@...il.com>
Reported-by: Debdeep Mukhopadhyay <debdeep.mukhopadhyay@...il.com>
Suggested-by: Linus Torvalds <torvalds@...uxfoundation.org>
Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
---
v2 -> v3:
- Public review
- Relies entirely on access_ok() for overflow checks as suggested
- Check against zero registersted pages is kept
- Replaced Suggested-by tag
v1 -> v2:
- Non-public review
- Added access_ok() and overflow check with roundup()
drivers/tee/tee_shm.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index f2b1bcefcadd..a88669d6ea68 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -240,6 +240,14 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
void *ret;
int rc;
+ addr = untagged_addr(addr);
+ start = rounddown(addr, PAGE_SIZE);
+ num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
+
+ /* Error out early if no pages are to be registered */
+ if (!num_pages)
+ return ERR_PTR(-EINVAL);
+
if (!tee_device_get(teedev))
return ERR_PTR(-EINVAL);
@@ -261,11 +269,8 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
shm->flags = flags;
shm->ctx = ctx;
shm->id = id;
- addr = untagged_addr(addr);
- start = rounddown(addr, PAGE_SIZE);
shm->offset = addr - start;
shm->size = length;
- num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
if (!shm->pages) {
ret = ERR_PTR(-ENOMEM);
@@ -326,6 +331,9 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
void *ret;
int id;
+ if (!access_ok((void __user *)addr, length))
+ return ERR_PTR(-EFAULT);
+
mutex_lock(&teedev->mutex);
id = idr_alloc(&teedev->idr, NULL, 1, 0, GFP_KERNEL);
mutex_unlock(&teedev->mutex);
--
2.31.1
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