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authorGui-Dong Han <2045gemini@gmail.com>2024-01-05 13:24:12 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2024-01-25 14:33:37 -0800
commitc9fe83c03d64e60e3bdf4ec118dd391ced800125 (patch)
tree85d5c074edc23337763ae9d97fbb1ae236781cef
parentde099c9a3011451b5d0562f31f47aa29a38d0a44 (diff)
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usb: mon: Fix atomicity violation in mon_bin_vma_fault
commit 2dd23cc4d0e6aa55cf9fb3b05f2f4165b01de81c upstream. In mon_bin_vma_fault(): offset = vmf->pgoff << PAGE_SHIFT; if (offset >= rp->b_size) return VM_FAULT_SIGBUS; chunk_idx = offset / CHUNK_SIZE; pageptr = rp->b_vec[chunk_idx].pg; The code is executed without holding any lock. In mon_bin_vma_close(): spin_lock_irqsave(&rp->b_lock, flags); rp->mmap_active--; spin_unlock_irqrestore(&rp->b_lock, flags); In mon_bin_ioctl(): spin_lock_irqsave(&rp->b_lock, flags); if (rp->mmap_active) { ... } else { ... kfree(rp->b_vec); rp->b_vec = vec; rp->b_size = size; ... } spin_unlock_irqrestore(&rp->b_lock, flags); Concurrent execution of mon_bin_vma_fault() with mon_bin_vma_close() and mon_bin_ioctl() could lead to atomicity violations. mon_bin_vma_fault() accesses rp->b_size and rp->b_vec without locking, risking array out-of-bounds access or use-after-free bugs due to possible modifications in mon_bin_ioctl(). This possible bug is found by an experimental static analysis tool developed by our team, BassCheck[1]. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations. The above possible bug is reported when our tool analyzes the source code of Linux 6.2. To address this issue, it is proposed to add a spin lock pair in mon_bin_vma_fault() to ensure atomicity. With this patch applied, our tool never reports the possible bug, with the kernel configuration allyesconfig for x86_64. Due to the lack of associated hardware, we cannot test the patch in runtime testing, and just verify it according to the code logic. [1] https://sites.google.com/view/basscheck/ Fixes: 19e6317d24c2 ("usb: mon: Fix a deadlock in usbmon between ...") Cc: <stable@vger.kernel.org> Signed-off-by: Gui-Dong Han <2045gemini@gmail.com> Link: https://lore.kernel.org/r/20240105052412.9377-1-2045gemini@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/mon/mon_bin.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c
index 094e812e9e69..35483217b1f6 100644
--- a/drivers/usb/mon/mon_bin.c
+++ b/drivers/usb/mon/mon_bin.c
@@ -1247,14 +1247,19 @@ static vm_fault_t mon_bin_vma_fault(struct vm_fault *vmf)
struct mon_reader_bin *rp = vmf->vma->vm_private_data;
unsigned long offset, chunk_idx;
struct page *pageptr;
+ unsigned long flags;
+ spin_lock_irqsave(&rp->b_lock, flags);
offset = vmf->pgoff << PAGE_SHIFT;
- if (offset >= rp->b_size)
+ if (offset >= rp->b_size) {
+ spin_unlock_irqrestore(&rp->b_lock, flags);
return VM_FAULT_SIGBUS;
+ }
chunk_idx = offset / CHUNK_SIZE;
pageptr = rp->b_vec[chunk_idx].pg;
get_page(pageptr);
vmf->page = pageptr;
+ spin_unlock_irqrestore(&rp->b_lock, flags);
return 0;
}