Bug 2424962 (CVE-2023-54039)

Summary: CVE-2023-54039 kernel: can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-12-24 12:04:07 UTC 
In the Linux kernel, the following vulnerability has been resolved:

can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access

In the j1939_tp_tx_dat_new() function, an out-of-bounds memory access
could occur during the memcpy() operation if the size of skb->cb is
larger than the size of struct j1939_sk_buff_cb. This is because the
memcpy() operation uses the size of skb->cb, leading to a read beyond
the struct j1939_sk_buff_cb.

Updated the memcpy() operation to use the size of struct
j1939_sk_buff_cb instead of the size of skb->cb. This ensures that the
memcpy() operation only reads the memory within the bounds of struct
j1939_sk_buff_cb, preventing out-of-bounds memory access.

Additionally, add a BUILD_BUG_ON() to check that the size of skb->cb
is greater than or equal to the size of struct j1939_sk_buff_cb. This
ensures that the skb->cb buffer is large enough to hold the
j1939_sk_buff_cb structure.

[mkl: rephrase commit message]
Comment 1 Alexander B 2025-12-25 12:39:22 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122439-CVE-2023-54039-82a4@gregkh/T