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High severity7.1NVD Advisory· Published May 17, 2024· Updated May 12, 2026

CVE-2024-35849

CVE-2024-35849

Description

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

btrfs: fix information leak in btrfs_ioctl_logical_to_ino()

Syzbot reported the following information leak for in btrfs_ioctl_logical_to_ino():

BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x110 lib/usercopy.c:40 instrument_copy_to_user include/linux/instrumented.h:114 [inline] _copy_to_user+0xbc/0x110 lib/usercopy.c:40 copy_to_user include/linux/uaccess.h:191 [inline] btrfs_ioctl_logical_to_ino+0x440/0x750 fs/btrfs/ioctl.c:3499 btrfs_ioctl+0x714/0x1260 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:904 [inline] __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at: __kmalloc_large_node+0x231/0x370 mm/slub.c:3921 __do_kmalloc_node mm/slub.c:3954 [inline] __kmalloc_node+0xb07/0x1060 mm/slub.c:3973 kmalloc_node include/linux/slab.h:648 [inline] kvmalloc_node+0xc0/0x2d0 mm/util.c:634 kvmalloc include/linux/slab.h:766 [inline] init_data_container+0x49/0x1e0 fs/btrfs/backref.c:2779 btrfs_ioctl_logical_to_ino+0x17c/0x750 fs/btrfs/ioctl.c:3480 btrfs_ioctl+0x714/0x1260 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:904 [inline] __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Bytes 40-65535 of 65536 are uninitialized Memory access of size 65536 starts at ffff888045a40000

This happens, because we're copying a 'struct btrfs_data_container' back to user-space. This btrfs_data_container is allocated in 'init_data_container()' via kvmalloc(), which does not zero-fill the memory.

Fix this by using kvzalloc() which zeroes out the memory on allocation.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

The Linux kernel's btrfs filesystem leaks uninitialized kernel heap memory to userspace through the btrfs_ioctl_logical_to_ino ioctl, allowing local information disclosure.

Vulnerability

The btrfs_ioctl_logical_to_ino() function in the Linux kernel's btrfs filesystem allocates a data container buffer using kvmalloc() without properly zeroing the allocated memory. When this buffer is subsequently copied to userspace via copy_to_user(), uninitialized kernel heap memory—up to 65536 bytes—is leaked. This bug was reported by syzbot through a KMSAN kernel-infoleak warning [1].

Exploitation

A local attacker with access to a btrfs filesystem can trigger the vulnerable ioctl by sending a crafted BTRFS_IOC_LOGICAL_TO_INO request. No authentication beyond the ability to open a btrfs file descriptor is required. The attacker can then read the leaked kernel heap data, which may contain sensitive information such as pointers, file contents, or cryptographic keys.

Impact

Successful exploitation results in an information disclosure of kernel heap memory. The leak can expose security-sensitive data from other processes or the kernel itself, aiding in further attacks like privilege escalation or bypassing KASLR. The severity is rated High with a CVSS v3 score of 7.1.

Mitigation

The vulnerability has been patched in mainline Linux kernel commits and backported to stable branches. Users should apply the latest kernel updates from their distribution. Affected products include the Siemens SIMATIC S7-1500 TM MFP GNU/Linux subsystem, which is impacted by this CVE among others [1].

References
  1. SSA-265688

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

119

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

11

News mentions

0

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