File metadata control #11
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l0kod
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Sep 9, 2024
[ Upstream commit a699781 ] A sysfs reader can race with a device reset or removal, attempting to read device state when the device is not actually present. eg: [exception RIP: qed_get_current_link+17] #8 [ffffb9e4f2907c48] qede_get_link_ksettings at ffffffffc07a994a [qede] #9 [ffffb9e4f2907cd8] __rh_call_get_link_ksettings at ffffffff992b01a3 #10 [ffffb9e4f2907d38] __ethtool_get_link_ksettings at ffffffff992b04e4 #11 [ffffb9e4f2907d90] duplex_show at ffffffff99260300 #12 [ffffb9e4f2907e38] dev_attr_show at ffffffff9905a01c #13 [ffffb9e4f2907e50] sysfs_kf_seq_show at ffffffff98e0145b #14 [ffffb9e4f2907e68] seq_read at ffffffff98d902e3 #15 [ffffb9e4f2907ec8] vfs_read at ffffffff98d657d1 #16 [ffffb9e4f2907f00] ksys_read at ffffffff98d65c3f #17 [ffffb9e4f2907f38] do_syscall_64 at ffffffff98a052fb crash> struct net_device.state ffff9a9d21336000 state = 5, state 5 is __LINK_STATE_START (0b1) and __LINK_STATE_NOCARRIER (0b100). The device is not present, note lack of __LINK_STATE_PRESENT (0b10). This is the same sort of panic as observed in commit 4224cfd ("net-sysfs: add check for netdevice being present to speed_show"). There are many other callers of __ethtool_get_link_ksettings() which don't have a device presence check. Move this check into ethtool to protect all callers. Fixes: d519e17 ("net: export device speed and duplex via sysfs") Fixes: 4224cfd ("net-sysfs: add check for netdevice being present to speed_show") Signed-off-by: Jamie Bainbridge <[email protected]> Link: https://patch.msgid.link/8bae218864beaa44ed01628140475b9bf641c5b0.1724393671.git.jamie.bainbridge@gmail.com Signed-off-by: Jakub Kicinski <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
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We should be able to control access to file metadata (e.g.
chmod,chgrp,setxattr,getxattr,utime). Some path-based LSM hooks enable to control a subset of these modifications, but we should provide users a safe and simple way to group these accesses, like with the following access rights:LANDLOCK_ACCESS_FS_READ_METADATA: read any file/dir metadata;LANDLOCK_ACCESS_FS_WRITE_SAFE_METADATA: change file times, user xattr;LANDLOCK_ACCESS_FS_WRITE_UNSAFE_METADATA: interpreted by the kernel, mostly xattr/chmod/chown that could change non-Landlock DAC or MAC, which could be considered as a policy bypass, or other various xattr that might be interpreted by filesystems. This should be denied most of the time.This work depends on #9.
See https://lore.kernel.org/all/Ywpw66EYRDTQIyTx@nuc/
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