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kmod/core: ensure the readonly flag is reset correctly

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When the core module loops through an object's list of dynrelas, it
determines whether or not the target location of the dynrela is in a
read-only region of the patch module. If it is, the readonly flag is set to
1 and it calls set_memory_{rw,ro} before and after the probe_kernel_write()
operation. This flag gets set once, and never gets reset for subsequent
iterations. Therefore, if a target happens to be in a RW section of the
patch module, and readonly = 1 had been set before, we may unintentionally
set a normally RW page to RO. Fix this by setting the readonly flag with
each iteration of the loop.

Fixes #681.
This commit is contained in:
Jessica Yu 2017-03-02 17:29:38 -08:00
parent 6ae49e36be
commit a095b4ed41
1 changed files with 2 additions and 3 deletions
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5
kmod/core/core.c
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@ -681,11 +681,10 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod,
( LINUX_VERSION_CODE >= KERNEL_VERSION(4, 4, 0) && \
UTS_UBUNTU_RELEASE_ABI >= 7 ) \
)
if (loc < core + kpmod->mod->core_layout.ro_size)
readonly = (loc < core + kpmod->mod->core_layout.ro_size);
#else
if (loc < core + kpmod->mod->core_ro_size)
readonly = (loc < core + kpmod->mod->core_ro_size);
#endif
readonly = 1;
#endif
numpages = (PAGE_SIZE - (loc & ~PAGE_MASK) >= size) ? 1 : 2;