Vulnerability CVE-2024-42315


Published: 2024-08-17

Description:
In the Linux kernel, the following vulnerability has been resolved:

exfat: fix potential deadlock on __exfat_get_dentry_set

When accessing a file with more entries than ES_MAX_ENTRY_NUM, the bh-array
is allocated in __exfat_get_entry_set. The problem is that the bh-array is
allocated with GFP_KERNEL. It does not make sense. In the following cases,
a deadlock for sbi->s_lock between the two processes may occur.

CPU0 CPU1
---- ----
kswapd
balance_pgdat
lock(fs_reclaim)
exfat_iterate
lock(&sbi->s_lock)
exfat_readdir
exfat_get_uniname_from_ext_entry
exfat_get_dentry_set
__exfat_get_dentry_set
kmalloc_array
...
lock(fs_reclaim)
...
evict
exfat_evict_inode
lock(&sbi->s_lock)

To fix this, let's allocate bh-array with GFP_NOFS.

 References:
https://git.kernel.org/stable/c/a7ac198f8dba791e3144c4da48a5a9b95773ee4b
https://git.kernel.org/stable/c/1d1970493c289e3f44b9ec847ed26a5dbdf56a62
https://git.kernel.org/stable/c/89fc548767a2155231128cb98726d6d2ea1256c9

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