In the Linux kernel, the following vulnerability has been resolved:
erofs: handle overlapped pclusters out of crafted images properly
syzbot reported a task hang issue due to a deadlock case where it is
waiting for the folio lock of a cached folio that will be used for
cache I/Os.
After looking into the crafted fuzzed image, I found it's formed with
several overlapped big pclusters as below:
Ext: logical offset | length : physical offset | length
0: 0.. 16384 | 16384 : 151552.. 167936 | 16384
1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384
2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384
...
Here, extent 0/1 are physically overlapped although it's entirely
_impossible_ for normal filesystem images generated by mkfs.
First, managed folios containing compressed data will be marked as
up-to-date and then unlocked immediately (unlike in-place folios) when
compressed I/Os are complete. If physical blocks are not submitted in
the incremental order, there should be separate BIOs to avoid dependency
issues. However, the current code mis-arranges z_erofs_fill_bio_vec()
and BIO submission which causes unexpected BIO waits.
Second, managed folios will be connected to their own pclusters for
efficient inter-queries. However, this is somewhat hard to implement
easily if overlapped big pclusters exist. Again, these only appear in
fuzzed images so let's simply fall back to temporary short-lived pages
for correctness.
Additionally, it justifies that referenced managed folios cannot be
truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy
up `struct z_erofs_bvec`") for simplicity although it shouldn't be any
difference.
Metrics
Affected Vendors & Products
References
History
Thu, 24 Oct 2024 14:45:00 +0000
Type | Values Removed | Values Added |
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Weaknesses | CWE-404 | |
Metrics |
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threat_severity
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Wed, 23 Oct 2024 22:30:00 +0000
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First Time appeared |
Linux
Linux linux Kernel |
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Weaknesses | CWE-667 | |
CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
Vendors & Products |
Linux
Linux linux Kernel |
Tue, 22 Oct 2024 01:30:00 +0000
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References |
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Metrics |
threat_severity
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cvssV3_1
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Mon, 21 Oct 2024 13:15:00 +0000
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ssvc
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Mon, 21 Oct 2024 12:30:00 +0000
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Description | In the Linux kernel, the following vulnerability has been resolved: erofs: handle overlapped pclusters out of crafted images properly syzbot reported a task hang issue due to a deadlock case where it is waiting for the folio lock of a cached folio that will be used for cache I/Os. After looking into the crafted fuzzed image, I found it's formed with several overlapped big pclusters as below: Ext: logical offset | length : physical offset | length 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384 ... Here, extent 0/1 are physically overlapped although it's entirely _impossible_ for normal filesystem images generated by mkfs. First, managed folios containing compressed data will be marked as up-to-date and then unlocked immediately (unlike in-place folios) when compressed I/Os are complete. If physical blocks are not submitted in the incremental order, there should be separate BIOs to avoid dependency issues. However, the current code mis-arranges z_erofs_fill_bio_vec() and BIO submission which causes unexpected BIO waits. Second, managed folios will be connected to their own pclusters for efficient inter-queries. However, this is somewhat hard to implement easily if overlapped big pclusters exist. Again, these only appear in fuzzed images so let's simply fall back to temporary short-lived pages for correctness. Additionally, it justifies that referenced managed folios cannot be truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy up `struct z_erofs_bvec`") for simplicity although it shouldn't be any difference. | |
Title | erofs: handle overlapped pclusters out of crafted images properly | |
References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-10-21T12:14:06.530Z
Updated: 2024-12-19T09:27:05.136Z
Reserved: 2024-09-30T16:00:12.958Z
Link: CVE-2024-47736
Vulnrichment
Updated: 2024-10-21T12:59:53.421Z
NVD
Status : Analyzed
Published: 2024-10-21T13:15:03.737
Modified: 2024-10-23T22:15:03.950
Link: CVE-2024-47736
Redhat