fkie_cve-2025-39901
Vulnerability from fkie_nvd
Published
2025-10-01 08:15
Modified
2025-10-02 19:12
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
i40e: remove read access to debugfs files
The 'command' and 'netdev_ops' debugfs files are a legacy debugging
interface supported by the i40e driver since its early days by commit
02e9c290814c ("i40e: debugfs interface").
Both of these debugfs files provide a read handler which is mostly useless,
and which is implemented with questionable logic. They both use a static
256 byte buffer which is initialized to the empty string. In the case of
the 'command' file this buffer is literally never used and simply wastes
space. In the case of the 'netdev_ops' file, the last command written is
saved here.
On read, the files contents are presented as the name of the device
followed by a colon and then the contents of their respective static
buffer. For 'command' this will always be "<device>: ". For 'netdev_ops',
this will be "<device>: <last command written>". But note the buffer is
shared between all devices operated by this module. At best, it is mostly
meaningless information, and at worse it could be accessed simultaneously
as there doesn't appear to be any locking mechanism.
We have also recently received multiple reports for both read functions
about their use of snprintf and potential overflow that could result in
reading arbitrary kernel memory. For the 'command' file, this is definitely
impossible, since the static buffer is always zero and never written to.
For the 'netdev_ops' file, it does appear to be possible, if the user
carefully crafts the command input, it will be copied into the buffer,
which could be large enough to cause snprintf to truncate, which then
causes the copy_to_user to read beyond the length of the buffer allocated
by kzalloc.
A minimal fix would be to replace snprintf() with scnprintf() which would
cap the return to the number of bytes written, preventing an overflow. A
more involved fix would be to drop the mostly useless static buffers,
saving 512 bytes and modifying the read functions to stop needing those as
input.
Instead, lets just completely drop the read access to these files. These
are debug interfaces exposed as part of debugfs, and I don't believe that
dropping read access will break any script, as the provided output is
pretty useless. You can find the netdev name through other more standard
interfaces, and the 'netdev_ops' interface can easily result in garbage if
you issue simultaneous writes to multiple devices at once.
In order to properly remove the i40e_dbg_netdev_ops_buf, we need to
refactor its write function to avoid using the static buffer. Instead, use
the same logic as the i40e_dbg_command_write, with an allocated buffer.
Update the code to use this instead of the static buffer, and ensure we
free the buffer on exit. This fixes simultaneous writes to 'netdev_ops' on
multiple devices, and allows us to remove the now unused static buffer
along with removing the read access.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni40e: remove read access to debugfs files\n\nThe \u0027command\u0027 and \u0027netdev_ops\u0027 debugfs files are a legacy debugging\ninterface supported by the i40e driver since its early days by commit\n02e9c290814c (\"i40e: debugfs interface\").\n\nBoth of these debugfs files provide a read handler which is mostly useless,\nand which is implemented with questionable logic. They both use a static\n256 byte buffer which is initialized to the empty string. In the case of\nthe \u0027command\u0027 file this buffer is literally never used and simply wastes\nspace. In the case of the \u0027netdev_ops\u0027 file, the last command written is\nsaved here.\n\nOn read, the files contents are presented as the name of the device\nfollowed by a colon and then the contents of their respective static\nbuffer. For \u0027command\u0027 this will always be \"\u003cdevice\u003e: \". For \u0027netdev_ops\u0027,\nthis will be \"\u003cdevice\u003e: \u003clast command written\u003e\". But note the buffer is\nshared between all devices operated by this module. At best, it is mostly\nmeaningless information, and at worse it could be accessed simultaneously\nas there doesn\u0027t appear to be any locking mechanism.\n\nWe have also recently received multiple reports for both read functions\nabout their use of snprintf and potential overflow that could result in\nreading arbitrary kernel memory. For the \u0027command\u0027 file, this is definitely\nimpossible, since the static buffer is always zero and never written to.\nFor the \u0027netdev_ops\u0027 file, it does appear to be possible, if the user\ncarefully crafts the command input, it will be copied into the buffer,\nwhich could be large enough to cause snprintf to truncate, which then\ncauses the copy_to_user to read beyond the length of the buffer allocated\nby kzalloc.\n\nA minimal fix would be to replace snprintf() with scnprintf() which would\ncap the return to the number of bytes written, preventing an overflow. A\nmore involved fix would be to drop the mostly useless static buffers,\nsaving 512 bytes and modifying the read functions to stop needing those as\ninput.\n\nInstead, lets just completely drop the read access to these files. These\nare debug interfaces exposed as part of debugfs, and I don\u0027t believe that\ndropping read access will break any script, as the provided output is\npretty useless. You can find the netdev name through other more standard\ninterfaces, and the \u0027netdev_ops\u0027 interface can easily result in garbage if\nyou issue simultaneous writes to multiple devices at once.\n\nIn order to properly remove the i40e_dbg_netdev_ops_buf, we need to\nrefactor its write function to avoid using the static buffer. Instead, use\nthe same logic as the i40e_dbg_command_write, with an allocated buffer.\nUpdate the code to use this instead of the static buffer, and ensure we\nfree the buffer on exit. This fixes simultaneous writes to \u0027netdev_ops\u0027 on\nmultiple devices, and allows us to remove the now unused static buffer\nalong with removing the read access."
}
],
"id": "CVE-2025-39901",
"lastModified": "2025-10-02T19:12:17.160",
"metrics": {},
"published": "2025-10-01T08:15:32.860",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/70d3dad7d5ad077965d7a63eed1942b7ba49bfb4"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/7d190963b80f4cd99d7008615600aa7cc993c6ba"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/9fcdb1c3c4ba134434694c001dbff343f1ffa319"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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