CVE-2022-50286— ext4: fix delayed allocation bug in ext4_clu_mapped for bigalloc + inline

ext4: fix delayed allocation bug in ext4_clu_mapped for bigalloc + inline

In the Linux kernel, the following vulnerability has been resolved: ext4: fix delayed allocation bug in ext4_clu_mapped for bigalloc + inline When converting files with inline data to extents, delayed allocations made on a file system created with both the bigalloc and inline options can result in invalid extent status cache content, incorrect reserved cluster counts, kernel memory leaks, and potential kernel panics. With bigalloc, the code that determines whether a block must be delayed allocated searches the extent tree to see if that block maps to a previously allocated cluster. If not, the block is delayed allocated, and otherwise, it isn't. However, if the inline option is also used, and if the file containing the block is marked as able to store data inline, there isn't a valid extent tree associated with the file. The current code in ext4_clu_mapped() calls ext4_find_extent() to search the non-existent tree for a previously allocated cluster anyway, which typically finds nothing, as desired. However, a side effect of the search can be to cache invalid content from the non-existent tree (garbage) in the extent status tree, including bogus entries in the pending reservation tree. To fix this, avoid searching the extent tree when allocating blocks for bigalloc + inline files that are being converted from inline to extent mapped.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ext4_clu_mapped函数在bigalloc和inline选项同时启用时错误搜索不存在的extent树，可能导致无效的extent状态缓存、错误的保留集群计数、内存泄漏和内核崩溃。

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