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This patch fixes a race condition between two functions that try to access the same inode. Since the i_mutex lock is held and released separately in the two functions, there may be the possibility that a violation is not correctly detected. Suppose there are two processes, A (reader) and B (writer), if the following sequence happens: A: ima_rdwr_violation_check() B: ima_rdwr_violation_check() B: process_measurement() B: starts writing the inode A: process_measurement() the ToMToU violation (a reader may be accessing a content different from that measured, due to a concurrent modification by a writer) will not be detected. To avoid this issue, the violation check and the measurement must be done atomically. This patch fixes the problem by moving the violation check inside process_measurement() when the i_mutex lock is held. Differently from the old code, the violation check is executed also for the MMAP_CHECK hook (other than for FILE_CHECK). This allows to detect ToMToU violations that are possible because shared libraries can be opened for writing while they are in use (according to the output of 'man mmap', the mmap() flag MAP_DENYWRITE is ignored). Changes in v5 (Roberto Sassu): * get iint if action is not zero * exit process_measurement() after the violation check if action is zero * reverse order process_measurement() exit cleanup (Mimi) Changes in v4 (Dmitry Kasatkin): * iint allocation is done before calling ima_rdrw_violation_check() (Suggested-by Mimi) * do not check for violations if the policy does not contain 'measure' rules (done by Roberto Sassu) Changes in v3 (Dmitry Kasatkin): * no violation checking for MMAP_CHECK function in this patch * remove use of filename from violation * removes checking if ima is enabled from ima_rdrw_violation_check * slight style change Suggested-by: Dmitry Kasatkin <d.kasatkin@samsung.com> Signed-off-by: Roberto Sassu <roberto.sassu@polito.it> Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> |
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| .. | ||
| evm | ||
| ima | ||
| digsig_asymmetric.c | ||
| digsig.c | ||
| iint.c | ||
| integrity_audit.c | ||
| integrity.h | ||
| Kconfig | ||
| Makefile | ||