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bb59d6895f
We make two glyphsets, GS1 and GS2, both with the same format depth. GS1 contains any glyph different from the others, let's call it U (unique). GS2 contains two glyphs with the same content, or at least sha1 hash. Let's call them A and B. We first register GS1 and GS2. GS1 has no problems, but before the fix, registering GS2 breaks accounting in `globalGlyphs`. Since there is no check for duplicate glyphs within a single set, we make two `GlyphNew` entries for A and B. Now in the loop at the end, we go over each entry and call `AddGlyph` and `FreeGlyph`: 1. AddGlyph(GS2, A, idA) inserts A into `globalGlyphs` 2. FreeGlyph(A) drops A's refcnt by one, but as it's being held in `globalGlyphs` it's kept alive. 3. AddGlyph(GS2, B, idB) finds A in `globalGlyphs` and reuses it instead of inserting B 4. FreeGlyph(B) drops B's refcnt by one (to zero), and B is freed. Before the fix, the lookup in `globalGlyphs` finds A's entry, and since it isn't a DeletedGlyph, it erroneously removes the `gr->glyph` pointing to `A` and decrements `tableEntries`. This results in `tableEntries` being off-by-one as `A` is still alive. Now, we free the glyphsets in a particular order. Freeing GS1 results in calling FreeGlyph(U), which will decrement U's refcnt to zero, and free U. This clears out the entry in `globalGlyphs` for U and decrements `tableEntries`, which due to the earlier error is now zero. When `FreeGlyphSet` sees this, it clears the `globalGlyphs` for that format depth. Now freeing A or GS2 (which transitively frees A) will try to check the `globalGlyphs` at that format depth, but because it was cleared out this crashes. The fix here is to change FreeGlyph to only free a glyph from `globalGlyphs` that is exactly the glyph being freed, so that FreeGlyph(B) doesn't touch `globalGlyphs` at all. This keeps a proper count in `tableEntries` and prevents `globalGlyphs[fdepth]` from being freed before A is freed. Closes: #1881 Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2264> (cherry picked from commit 81edc9caf557f7a44c5b308742814457de0eb6c0) (cherry picked from commit 716d876142280cd66bdcf000f81428dadd5d3937) Signed-off-by: Octavia Togami <octy@octyl.net> |
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| .. | ||
| bigreq | ||
| bugs | ||
| damage | ||
| info | ||
| pyxtest | ||
| scripts | ||
| sync | ||
| xi1 | ||
| xi2 | ||
| .gitignore | ||
| ddc-tests.c | ||
| fixes.c | ||
| hashtabletest.c | ||
| input.c | ||
| list.c | ||
| list_zeroinit.c | ||
| meson.build | ||
| misc.c | ||
| README | ||
| sha1.c | ||
| signal-logging.c | ||
| simple-xinit.c | ||
| string.c | ||
| test_xkb.c | ||
| tests-common.c | ||
| tests-common.h | ||
| tests.c | ||
| tests.h | ||
| touch.c | ||
| xfree86.c | ||
| xtest.c | ||
X server test suite This suite contains a set of tests to verify the behaviour of functions used internally to the server. = How it works = Through some automake abuse, we link the test programs with the same static libraries as the Xorg binary. The test suites can then call various functions and verify their behaviour - without the need to start the server or connect clients. This testing only works for functions that do not rely on a particular state of the X server. Unless the test suite replicates the expected state, which may be difficult. = How to run the tests = Run "make check" in the test directory. This will compile the tests and execute them in the order specified in the TESTS variable in test/Makefile.am. Each set of tests related to a subsystem are available as a binary that can be executed directly. For example, run "xkb" to perform some xkb-related tests. == Adding a new test == When adding a new test, ensure that you add a short description of what the test does and what the expected outcome is.