Описание
In the Linux kernel, the following vulnerability has been resolved:
configfs_lookup(): don't leave ->s_dentry dangling on failure
Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all.
We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it.
However, for configfs_lookup() it does survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry.
Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free......
In the Linux kernel, the following vulnerability has been resolved:
configfs_lookup(): don't leave ->s_dentry dangling on failure
Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all.
We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it.
However, for configfs_lookup() it does survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry.
Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free...
This is the minimal fix; the right approach is to set the linkage between dentry and configfs_dirent only after we know that we have an inode, but that takes more surgery and the bug had been there since 2006, so...
Ссылки
- https://nvd.nist.gov/vuln/detail/CVE-2026-74359
- https://git.kernel.org/stable/c/10da12d352b7b2bb330a8609fdda9a58bf0e9856
- https://git.kernel.org/stable/c/3e83b2203aa59bd279e4f677ec793d49dc9d019e
- https://git.kernel.org/stable/c/57088b06109f3222963c639d8d743f42c2899b13
- https://git.kernel.org/stable/c/9c747dcee164ead300de90550ad9e4122f0d1bbb
- https://git.kernel.org/stable/c/b6e9c82522ddaa3ac0706b295ff4a71975d4f883
- https://git.kernel.org/stable/c/c3b073a209a9baa691b744318ac929fecdd8847c
- https://git.kernel.org/stable/c/eee07d769da5ac4e4f7bd0bc17828646a318d499
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: configfs_lookup(): don't leave ->s_dentry dangling on failure Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all. We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it. However, for configfs_lookup() it *does* survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry. Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free... This...
In the Linux kernel, the following vulnerability has been resolved: configfs_lookup(): don't leave ->s_dentry dangling on failure Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all. We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it. However, for configfs_lookup() it *does* survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry. Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free... This...
In the Linux kernel, the following vulnerability has been resolved: configfs_lookup(): don't leave ->s_dentry dangling on failure Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all. We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it. However, for configfs_lookup() it *does* survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry. Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free... T
In the Linux kernel, the following vulnerability has been resolved: c ...